Mistake in README

[binarybana]

The warning in the README about the typesafety of integers is still correct in general, but the note about this being important for dictionaries is not. Since Julia now hashes integer values (no matter the type) as being the same, this is not a big concern for dictionaries:

julia> isequal(5,uint64(5))
true

julia> hash(5)
0x0583d46ff02a00ec

julia> hash(uint8(5))
0x0583d46ff02a00ec

[sbillig]

Fixed, thanks.