Merge pull request #672 from guard/rework_deprecations

Rework deprecations
fix feature regexp
refactor Rakefile
rework stubs (IO, Pathname, EVN)
cover missing case with spec
enforce better stubbing + fix specs
deprecate match_guardfile
move reevaluate to Reevaluator
remove unneeded namespace
rework evaluator and spec
implement Dsl.evaluate
rework generator
rework Cli
fix requires (watcher)