Fix documentation of IO module
Merge pull request #2803 from dskecse/fix-io-docs

Fix documentation of IO module
Don't crash on malformed proxy env var
Refactor and add new rewrite rules
Purge and delete modules before compiling them
Also purge and delete during tests
Test that we do purge and delete artifacts
downcase path comparison in application directory test
Merge pull request #2808 from jw2013/master

Downcase path comparison in application directory test

On case insensitive operating systems like Mac OS X, the path stored
by the code server may not match the case of the one from System.cwd!
Write to manifest when file is removed
--elixirc-paths should be a subset of project paths

Since the manifest is shared, --elixirc-paths must
be a subset as we need to know what to change and what
to not change in the manifest file.
Add task for pushing standalone mix
Fix String.replace/4 typespec
Build .beam location from scratch on mix compile.elixir
Remove unecessary comment
 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