Introduce `StringIO.flush/1` function
Support mix help --search PATTERN
 Add OTP 17.3 to run on Travis CI
Merge pull request #2812 from edgurgel/patch-1

 Add OTP 17.3 to run on Travis CI
Make the parameter more explicit
Fix a couple of minor typos in docstrings
Merge pull request #2813 from citizenparker/master

Fix a couple of minor typos in docstrings
No longer inline binary expressions in EEx

String.Chars is now always inlined by the compiler.

Closes #2815
fix typo
Merge pull request #2816 from jw2013/typo

fix typos
Fix missing concatenation operator.
Fix test for mix deps.clean.
Merge pull request #2819 from benjamintanweihao/patch-3

Fix missing concatenation operator.
set null prompt function in dumbterm mode
Merge pull request #2821 from k1complete/shown_prompt_erlsh_in_dumbterm

set null prompt function in dumb term mode
Do not set not shell as we know have a custom prompt
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
fix typos