Typos and whitespace fixes in README.md
Add `clean` target to Makefile
Get rid of warning

    include/nvp.h:28:23: warning: inline function 'virtual void hiberlite::abstract_atom::bindValue(sqlite3_stmt*, int)' used but never defined [enabled by default]
Get rid of signedness warnings
Merge pull request #8 from sschober/master

Clean compile on GCC 4.8.2 and README.md typo fixes