Make Char no longer a subtype of Integer

I feel that this is surprising behavior, and this issue has come up in #5844 and #8569.

All the tests pass  except for readlm and parallel (which hangs forever).  I guess I'm looking for a up / down vote on this (breaking) behavior before fixing the last remaining issues. 
Seems like that's how it is [implemented](https://github.com/JuliaLang/julia/pull/8816/files#diff-5e7171f7c2c327992a2bbabffd6ea3b7R46)