fix #9: add floating precision attribute
fix #8: refactoring, API cleaning and test suite

includes:
 - use new-style properties
 - move consistency checks over to setters
 - cleaning and refactoring
 - update test suite
fix #10: add option to precompute at construct time
move version over to setup script
update documentation
bump development version
fix #11: absolute import now working
fix #12: remove conflicting test case for now
simplify the package API further
bump release version to 1.2.1