Silence Gemfile warnings
Update for Ruby 2.1.3

Will want to upgrade RSpec separately, but it was freaking out about the
pending specs. With this, the test suite is clean.
Update copyright and authorship info
Remove donations section from docs

This was just cluttering things up.
Put license boilerplate on a diet

For similar reasons to those stated in commit
6cd8d28d57e991d2db17196f5d2ec214df85ee1c in the Command-T repo.
doc: describe new version requirements
Update to RSpec 3.1.0

Surprisingly, little broke in the move from 1.3.0 to 3.1.0. Changes
included:

- simplify `require 'spec_helper'` statements
- kill some old lambdas
- change `expect`/`should` assertions to `expect`/`to`
- updates for new mock API
- update binstubs
- drop explicit `require 'rubygems'` from spec helper; we'll always run
  using `bin/rspec`
- tweak `pending` examples, as RSpec now complains if they have a block
  which doesn't raise an error

Note, we're still mostly using the deprecated `should` syntax. I'll
leave the move to `expect` for another moment.
Update Rspec syntax

Did this with the help of the transpec gem. Contrary to the README, I
found I did need to add it to the Gemfile (although obviously, I removed
it immediately afterwards).

Additionally it crashed trying to open `.git/COMMIT_EDITMSG` after the
conversion had completed, because I was running it from inside a
submodule; upstream issue for that:

  https://github.com/yujinakayama/transpec/issues/94

Here are the relevant bits of the output:

  Summary:

  415 conversions
    from: obj.should
      to: expect(obj).to
  382 conversions
    from: == expected
      to: eq(expected)
  100 conversions
    from: lambda { }.should
      to: expect { }.to
  35 conversions
    from: obj.should_not
      to: expect(obj).not_to
  32 conversions
    from: lambda { }.should_not
      to: expect { }.not_to
  2 conversions
    from: it { should_not ... }
      to: it { is_expected.not_to ... }
  1 conversion
    from: it { should ... }
      to: it { is_expected.to ... }

  967 conversions, 0 incompletes, 0 warnings, 0 errors

Sure beats doing it by hand, or even with Vim macros...
Don't shadow "proc" method

At some point, around 1.9 I think, `proc` became a shorthand for
`Proc.new`; we shouldn't be shadowing it in this way.
Bump version number to 0.2 in preparation for release

Will need a new version number so that Walrus can depend on it.
Apply a minor style fix to generated source for Node class
Simplify LocationTracking#rightmost?

- drop unnecessary explicit `self` receivers
- merge final two conditional clauses into one