ENH: add max/min version for simplifying version range comparisons.
BUG: fix min/max bound handling when not explicitly set in the spec.
BUG: make sure one can stringify min/max version.
FEAT: add str support for package for pretty-printing.
FEAT: add brute-force SAT solver.
ENH: ensure literal names are valid.
REF: set package's unique name as a property.
FEAT: add travis-ci (py 2.7 only for now).
DOC: mention that depsolver is strongly 'ahem' inspired by Composer.
REF: move specifiction definitions in separate module.