Ensure deps can run after mix deps.get
assert_receive(d) should leak

Closes #2030.
CaptureIO now returns an empty string instead of nil when there is no capture
Only raise on conflicts coming from functions
Updating Version specs, dialyzer warnings
Fixing doc typos in Version
Merge pull request #2050 from jwarwick/version_spec

Updated specs in Version
Fixing result handling of :file.consult
Fixed spec for Enum.flat_map
Release v0.12.4
Start v0.12.5-dev
Add guards to lstrip and rstrip
Emit warnings for using % as sigils
Automatically recompile on outdated elixir version
`mix deps.get` does not use MIX_ENV
Revert "`mix deps.get` does not use MIX_ENV"

This reverts commit 1e9cd551ce6fe2406e4b664a67faa8660d722201.
Make Mix.Utils.Underscore accept .'s and empty args
Made Mix.Utils.camelize handle empty string
Merge pull request #2057 from jwarwick/mix_underscore

Mix.Utils handling empty strings
Fix handling of raw rebar deps