Add missing require for thingatpt

beginning-of-thing is part of thingatpt
Add missing code section to comment front-matter
Add missing license section to comment front-matter
A few doc fixes
Merge remote-tracking branch 'bbatsov/style'
Touch up docstrings, change the signatures of inf-ruby-complete[-or-tab]

Because using the interactive form for code reuse is bad.
Add pry to inf-ruby-implementations