Merge pull request #17 from bugst/performance

Increase parsing and comparison performance

Updated license date

Merge pull request #15 from bugst/speedup

Speedup dependency resolver by analizying fruitless branches first

Merge pull request #14 from bugst/speedup_leaf_backtracking

Speedup dependency resolver by pre-cutting unsolvable branches

Merge pull request #12 from bugst/normalized_string

Added NormalizedString to be used as key in maps

Release 0.9.0