Convert README to Markdown [ci skip]
Small Gemfiles improvements
Update '.gitignore'
Merge pull request #95 from kuraga/patch2

Small Gemfiles improvements
Merge pull request #96 from kuraga/patch3

Update '.gitignore' (sync with cells)
Update Travis (sync with cells)
Merge pull request #97 from kuraga/markdown

Convert README to Markdown [ci skip]
Merge pull request #102 from kuraga/patch-3

Update Travis (sync with cells)