Bump version to 3.6.11
Merge branch 'release-3.6.x' of github.com:nanoc/nanoc into release-3.6.x

Conflicts:
	Gemfile.lock
Merge branch 'release-3.6.x'

Conflicts:
	Gemfile.lock
	NEWS.md
	lib/nanoc/version.rb
Upgrade dependencies
Merge branch 'release-3.6.x'

Conflicts:
	Gemfile.lock