Add erlang.mk
Add new Makefile for erlang.mk
Add typespecs for sfmt.erl and sfmt_pure.erl
Remove rebar and EUnit files
Add Makefile.sfmt
Update Makefile.sfmt to add new targets
Add new rules to Makefile

* target `clean` now includes cleaning up ./priv
* add target `c_doc` and `speed`
Add src/sfmt_{pure_}tests.erl

* Recover non-EUnit speed-testing code
* Add minimal typespecs
Update Makefile.sfmt to include target `nif` in target `deps`
Update .travis.yml with Common Test script
Change vsn to 0.10.0 at sfmt.app.src
Update CHANGES.md for 0.10.0
Change Makefile.sfmt to use Travis CI options for CC and CFLAGS