Speed up the compilation process v5

Sames as #113 except:

* trivial fixes and updates
* build info data refactoring
* using term_to_binary compression
* not writing build info file if the graph is unmodified
* default enabling keep_build_info
* unconditionally keeping build info
* making the info file universal and storing it as `<base_dir>/.rebarinfo`
* introducing `<base_dir>/.rebar/` and storing erlc build info there
* fixing regressions