Merge tag '0.10.1' into develop

0.10.1
shift gems to gemspec where they belong

Conflicts:
	Gemfile
	text2048.gemspec
Add development gems to bundler's test group.
Merge pull request #11 from yasuhito/feature/gem_dependency

Feature/gem dependency
RuboCop 0.23.0.
Update flog to 4.2.1.
Update flay to 2.5.0.
Versiom bump.
Merge branch 'release/0.10.2'