Merge pull request #1470 from ToJans/master

Updated windows elixir.bat to use -pa instead of -env ERL_LIBS
Only clean up manifest for files that were actually removed, closes #1440
Remove duplicate in erlang, leex and yecc compilers
Ensure sigils with no interpolation are fully expanded at compile time, closes #1471
Improve docs for ExUnit
Update mix test docs
Add the clear helper, which cleared the screen. Also introduced the convention that if a helper returns dont_display_result/0, then we skip the inspecting of the result. Changed the introspection helpers h, s, and t to use this.
Forgot the changelog
Fixed typos in Mix.Tasks.Compile.Erlang and Mix.Tasks.Test
Merge pull request #1474 from jwarwick/mix_typos

Fixed typos in Mix.Tasks.Compile.Erlang and Mix.Tasks.Test
Merge pull request #1473 from pragdave/iex-cls

Add the clear helper, which cleared the screen. Also introduced the ...
Tidy up IEx docs and tests
Clean up make clean
Include test time on trace results
Update CHANGELOG
Allow coverage tool to be pluggable
Add record type `Record.t`
Add String.to_char_list and String.from_char_list
Check ExUnit.Server is registered before adding cases, closes #1472
Merge pull request #1476 from meh/string-list

Add String.to_char_list and String.from_char_list