Allow CC to be defined other than gcc. If not defined, use gcc as default.
Added .travis.yml for continuous integration. Added env variable to disable AVX2 for Travis (GCC version doesn't support it yet).
Added -lrt to fix undefined references to clock_gettime on some systems
Test AVX2 on gcc-4.8 also
make it possible to add custom CFLAGS
version.h is no longer used
Merge pull request #88 from darealshinji/patch-2

version.h is no longer used
Makefile now compiles tests. Fixed test files. Removed unused stuff.
Configured Travis to run unit tests.
Removed duplicate consts.
Added Travis CI status image
Load greatest submodule. Fixed loop that occurred during build process.
Fix compilation on MinGW-w64.

Use getopt.h in system in preference to one in extras dir.