Line continuations for indentation, refs #102.

This adds a :line_continuations option to the indentation_spaces ruler,
allowing you to specify that a statement that spans multiple lines
should indent the second and subsequent lines.

You can enable line continuations by passing it as an option to
identation_spaces in your config:

  style.indentation_spaces 2, level: :error, line_continuations: true
Merged in acrmp:line-continuation.  Closes gh-143.
Randomize tests
Added nokogiri to the list of deps
Updated comments to reflect line_continuations changes

Relates to gh-143.
Let's do Ruby 2.1.0 too