Merge pull request #1 from hcs42/master

Find rebar.config by walking up the directories
Complete auto-imported BIFs
Complete modules

The rebar.config processing was rewritten just like in vim-erlang-compiler
commit 499ac6927968e3d70ea57e6604166423b64baf2f:

https://github.com/vim-erlang/vim-erlang-compiler/commit/499ac6927968e3d70ea57e6604166423b64baf2f
Add ../ebin to search path

This is useful when there is no rebar.config file, but we have the standard
code layout with an "src and an "ebin" directory.
Add "<rebar.config dir>/ebin" to the code path

This is useful when rebar.config is in the "apps" directory, and the "ebin"
directory is next to it.
Make parser a bit more lenient

In some cases, the simplify_return parameter can be {abstype, _, List}, where
List may have more than one element.