Use YARD for documentation.

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>
Save YARD docs in ./yardoc.

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>
Merge branch 'yard'

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>

Conflicts:
	.yardopts
	Gemfile