[BUGFIX] Remove Gemfile.lock.

Gemfile.lock must not be included in a gem as it needlessly narrows the
allowed versions of dependent gems, making the gem very hard to get to
work together with other gems.

Source:
http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/

Also add Gemfile.lock to .gitignore.
[TASK] Raise RVM and Gem minimum versions

- Add Ruby 2.1 to .travis.yml.
- Drop Ruby < 1.9.3 (all end-of-life versions) from .travis.yml.
- Make 1.9.3 the minimum required Ruby version.
- Make Rails 3.2.0 the minimum required version.
- Change the development requirement to Rake 10.3.2 (the current version).
- Drop any mentions of Rails 2.x from the README.
[BUGFIX] Fix a few typos in the README.
Merge pull request #4 from braingourmets/bugfix/typos

[BUGFIX] Fix a few typos in the README.
Merge pull request #1 from braingourmets/bugfix/remove-gemfile-lock

[BUGFIX] Remove Gemfile.lock.
Merge pull request #3 from braingourmets/cleanup/minimum-versions

[TASK] Raise RVM and Gem minimum versions