Initial IO.ANSI implementation (based on https://github.com/yrashk/ansiex)
Add a pre-R16 warning about ANSI escape sequences in iex/erl
Introduce IO.ANSI.escape/1,2 functions
Put proper IO.ANSI tests in
Improve IO.ANSI test case so it can be run on non-terminals correctly
IO.ANSI.escape implies terminating #[reset] now and IO.ANSI.escape_fragment has been introduced
Merge pull request #775 from yrashk/io-ansi

Initial IO.ANSI implementation (based on https://github.com/yrashk/ansiex)