Merge pull request #164 from graysonwright/minitest_dependency

New Minitest has breaking API changes, revert to 4.6.X
skipping view model tests for now.
Remove 'about.yml' as a redundant file
Update 'Rakefile': update default task's desc
Update '.gitignore'
Merge pull request #168 from kuraga/sync-with-apotomo

Sync with apotomo
Convert README to Markdown [ci skip]
Update Travis configuration
Merge pull request #170 from kuraga/markdown

Convert README to Markdown [ci skip]
remove jruby-head from CI.
Merge branch 'master' of github.com:apotonick/cells
Update Minitest version