update README

README.md

@@ -5,10 +5,8 @@
 [![Coverage Status](https://coveralls.io/repos/Jutho/WignerSymbols.jl/badge.svg?branch=master&service=github)](https://coveralls.io/github/Jutho/WignerSymbols.jl?branch=master)
 [![codecov.io](http://codecov.io/github/Jutho/WignerSymbols.jl/coverage.svg?branch=master)](http://codecov.io/github/Jutho/WignerSymbols.jl?branch=master)
 
-Compute Wigner's 3j and 6j symbols, and related quantities such as Clebsch-Gordan coefficients and Racah's symbols.
+Compute Wigner's 3j and 6j symbols, and related quantities such as Clebsch-Gordan
-
+coefficients and Racah's symbols.
-## Requirements
-Latest version is compatible with Julia v0.7 only, but older versions can be installed on Julia v0.6.
 
 ## Installation
 Install with the new package manager via `]add WignerSymbols` or
@@ -18,7 +16,8 @@ Pkg.add("WignerSymbols")
 ```
 
 ## Available functions
-While the following function signatures are probably self-explanatory, you can query help for them in the Julia REPL to get further details.
+While the following function signatures are probably self-explanatory, you can query help
+for them in the Julia REPL to get further details.
 *   `wigner3j(T::Type{<:AbstractFloat} = Float64, j₁, j₂, j₃, m₁, m₂, m₃ = -m₂-m₁) -> ::T`
 *   `wigner6j(T::Type{<:AbstractFloat} = Float64, j₁, j₂, j₃, j₄, j₅, j₆) -> ::T`
 *   `clebschgordan(T::Type{<:AbstractFloat} = Float64, j₁, m₁, j₂, m₂, j₃, m₃ = m₁+m₂) -> ::T`
@@ -27,20 +26,31 @@ While the following function signatures are probably self-explanatory, you can q
 *   `δ(j₁, j₂, j₃) -> ::Bool`
 *   `Δ(T::Type{<:AbstractFloat} = Float64, j₁, j₂, j₃) -> ::T`
 
-The package also defines the `HalfInteger` type that can be used to represent half-integer values. Construct if as `HalfInteger(a::Real)` or `HalfInteger(numerator::Integer, denominator::Integer)`. Furthermore, the range operator `a:b` can be used to create ranges of `HalfInteger` values (a `HalfIntegerRange`).
+~~The package also defines the `HalfInteger` type that can be used to represent half-
+integer values. Construct if as `HalfInteger(a::Real)` or `HalfInteger(numerator::Integer,
+denominator::Integer)`. Furthermore, the range operator `a:b` can be used to create ranges
+of `HalfInteger` values (a `HalfIntegerRange`).~~
+
+The package now relies on [HalfIntegers.jl](https://github.com/sostock/HalfIntegers.jl) to
+support and use arithmetic with half integer numbers.
 
 ## Implementation
 Largely based on reading the paper (but not the code):
 
 [1] [H. T. Johansson and C. Forssén, SIAM Journal on Scientific Compututing 38 (2016) 376-384](https://doi.org/10.1137/15M1021908) ([arXiv:1504.08329](https://arxiv.org/abs/1504.08329))
 
-with some additional modifications to further improve efficiency for large `j` (angular momenta quantum numbers).
+with some additional modifications to further improve efficiency for large `j` (angular
+momenta quantum numbers).
 
-In particular, 3j and 6j symbols are computed exactly, in the format `√(r) * s` where `r` and `s` are exactly computed as `Rational{BigInt}`,
+In particular, 3j and 6j symbols are computed exactly, in the format `√(r) * s` where `r`
-using an intermediate representation based on prime number factorization. As a consequence thereof, all of the above functions can be called
+and `s` are exactly computed as `Rational{BigInt}`, using an intermediate representation
-requesting `BigFloat` precision for the result. There is currently no convenient syntax for obtaining `r` and `s` directly (see TODO).
+based on prime number factorization. As a consequence thereof, all of the above functions
+can be called requesting `BigFloat` precision for the result. There is currently no
+convenient syntax for obtaining `r` and `s` directly (see TODO).
 
-Most intermediate calculations (prime factorizations of numbers and their factorials, conversion between prime powers and `BigInt`s) are cached to improve the efficiency, but this can result in large use of memory when querying Wigner symbols for large values of `j`.
+Most intermediate calculations (prime factorizations of numbers and their factorials,
+conversion between prime powers and `BigInt`s) are cached to improve the efficiency, but
+this can result in large use of memory when querying Wigner symbols for large values of `j`.
 
 Also uses ideas from
 
@@ -53,5 +63,5 @@ for caching the computed 3j and 6j symbols.
 
     [3] [L. Wei, New formula for 9-j symbols and their direct calculation, Computers in Physics, 12 (1998), 632–634.](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.481.5946&rep=rep1&type=pdf)
 
-*   Convenient syntax to get the exact results in the `√(r) * s` format, but in such a way that it can be used by
+*   Convenient syntax to get the exact results in the `√(r) * s` format, but in such a way
-    the Julia type system and can be converted afterwards.
+    that it can be used by the Julia type system and can be converted afterwards.