Add -I include/ to build-ct-suites target
Don't download index file

If all deps know where to download it, then don't download index file.
Update README to include multi dependency example
Merge branch 'patch-1' of git://github.com/yellow5/erlang.mk
Merge branch 'fix-test-include' of git://github.com/ahf/erlang.mk
Merge branch 'index_file' of git://github.com/nevar/erlang.mk
erlc: update {id, git} in .app.src with git describe output
Merge branch 'add-git-describe-to-id-field' of git://github.com/dch/erlang.mk
[inaka/elvis#96] Elvis plugin.
Merge branch 'jfacorro.elvis.96.plugin' of git://github.com/inaka/erlang.mk
Alphabetical order build.config
Don't distclean PKG_FILE2 if it's custom
Compile Makefile-free dependencies with +debug_info only

As much as I dislike this change, this should simplify the
process of moving to erlang.mk.
Allow overriding the method and directories analyzed by Dialyzer
Add an erlang-mk target for automated updating of erlang.mk