Minor gem related updates

Update all the things! This is a bit of clean up and a little new feature creep.

- Ignore bundler related files (allowing for the use of `--standalone`)
- Tighten up the gemspec a bit
  - Fill out the homepage and description (though it's a cheap copy of the summary)
  - Lock executables to a manual array; this allows for local development and test environments to use binstubs
  - Lock into Ruby 2.x
  - Move non-essential development gems into the Gemfile to group by
- Update RSpec config to keep the `spec/spec_helper.rb` fast and lightweight
  - Only `require` the minimum gems
  - Remove all custom support configs
- Increase the gem load time by using [`autoload`](http://ruby-doc.org/core-2.1.2/Kernel.html#method-i-autoload) instead of requiring all files up-front
- Fix Ruby warnings in `lib/` and `spec/` files
- New Feature: Allow environment to set defaults for the configuration