started porting the parser to use parslet gem
UnitParser was not parsing mixed-case units correctly

- Had to re-arrange the UnitParser sequence so that
  it tries to match case-insensitive variations before
  shorter variations (e.g. 'tSp' before 't')
Fixed container unit parsing
uncomment rest of spec examples. parslet is working yayyyy
remove pry-debugger as dev dependency
commented-out performanc spec..
fast regex unit parser prototype in performance_spec
Parens optional for containers, parse english words as amounts
Container amount separator can have a dash
Merge pull request #6 from djcp/parslet

Parser extensions and fixes
Update .travis.yml
Allow rubinius CI failures for now
Merge pull request #4 from iancanderson/parslet

Rewritten parser using Parslet