Introduce `StringIO.flush/1` function
Support mix help --search PATTERN
Merge pull request #2807 from pma/support_mix_help_search

Support mix help --search PATTERN
Merge pull request #2793 from lexmag/master

Introduce `StringIO.flush/1` function
Update CHANGELOG
Merge branch 'master' of https://github.com/elixir-lang/elixir