Ensure the same pid is not queued twice in the parallel compiler
There is no need to rely @on_definition callbacks to store tags
Ensure doctests run as expected
Update heredoc tests
Added Base module implementing base encoding functions according to RFC4648
Merge pull request #2137 from pma/v0.13

Added Base module with implementation for base 64 and base 16
Merge pull request #2096 from devinus/stringio

StringIO improvements
Rename StringIO API to be more IO like (start -> open, stop -> close)
Add Code.eval_file/2
Merge branch 'master' into v0.13-master
Update CHANGELOG
Support older gits in mix

Do not add `--progress` flag to `git fetch` command unless git version
is 1.7.1 or newer.
Merge pull request #2138 from elixir-lang/mix-old-git

Support older gits in mix
Ensure --help and mix help go through the same path, closes #2142
Show correct error if mix task could not be found
Remote converger should receive full dep struct
Unify precedence of when, ::  and |
Ensure tracing set default max cases to 1
Improve docs for Macro.expand/2
Fixed doc typos. Fixed unused function arg.