Improve cannot pipe error
Manually call check_command before eval, closes #2449
ErlangError -> CompileError
Do not remove interpolation escape on uppercase sigils, closes #2512
Only accept --no-SWITCH for booleans

The previous behaviour was confusing and a special case.
This enables negated switches only for booleans, otherwise
it is considered as a regular switch (as the combination
of --no-SWITCH for any other type is an error anyway).
Update changelog
Don't keep all in the option parser config
Add OptionParser.split/1
Use Keyword syntax instead of list check
Clarify elixirc_options are overridden via CLI
Only read mtime once per source file
Warn and reset mime on future files
Merge pull request #2513 from ericmj/mix-mtimes

Warn and reset mime on future files
Fix bug where umbrella tasks were not reenabled

Closes #2058.