Improve Enumerable count/member? docs
Change the Path module to work only with char_data and always return binaries
Convert File and IO to char data, use +fnu flag by default
Provide List.from_char_data! and String.from_char_data!
Rename iolist_* to iodata_*
Properly @spec functions in Path
Typespec and allow char data in File functions
Properly indent chunks in System module
Small grammar fix
Minor grammar tweak

Subject/verb agreement at the top
Merge pull request #2178 from augiedb/patch-2

Minor grammar tweak
Merge pull request #2177 from augiedb/patch-1

Small grammar fix
Proper error message for bad args to 'mix help'

Closes #2179.
Update example to use Map.put/3, accordingly with the last proposal

[Proposal 1](https://gist.github.com/josevalim/9acd0fe43063cbc33aa6)
has the update operation also put new keys in the map, while the
[2nd proposal](https://gist.github.com/josevalim/b30c881df36801611d13)
doesn't support this. The docs reflected the first proposal.
Merge pull request #2180 from MSch/docfix-special_forms-map

Docfix: Use Map.put/3 in Kernel.SpecialForms struct docs.
Spruce up the output format of ex_unit

Conflicts:
	lib/ex_unit/lib/ex_unit/assertions.ex
Clean up new formatter implementation
Reject __struct__ field on struct/2
Properly format and indent test output
Allow overriding of undefined dependency SCM

This allows a developer to override an unrecognized SCM without Mix
raising.