Dispatch on keyword arguments. It exports 2 macros:

`@kwdispatch`

designates a function signature to use for keyword dispatch`@kwmethod`

defines the method for the keyword argument

```
using KeywordDispatch
@kwdispatch f()
@kwmethod f(;a) = "a is $a"
@kwmethod f(;a::Integer) = "a is $a, and is an Integer"
@kwmethod f(;b) = "b is $b"
@kwmethod f(;a,b) = "a is $a, b is $b"
@kwmethod f(;) = "look mum, no args!"
```

at the REPL:

```
julia> f()
"look mum, no args!"
julia> f(a=1.0)
"a is 1.0"
julia> f(a=1)
"a is 1, and is an Integer"
julia> f(b=3,a=1)
"a is 1, b is 3"
```