Refactor

# Refactor

### Goal:
remove jeweler dependency and use bundler for gem management tasks

### Notes:
* Move to bundler: 
  - The gem is now setup to use bundler generated files and conventions
  - Use gemspec to specify **development** and **runtime** dependencies
  - use `lib/jumpstart_auth/version.rb` to manage versioning
* JumpstartAuth is now a module. 
  - This was the biggest change and was done to match conventions used by bundler for things like versioning.
* The main JumpstartAuth API should still work.
  - `JumpstartAuth.twitter` returns a twitter client that supports methods `[:friends, :followers, :update]`
* There are still no tests
* Given the size of the change and the previous bullet point I consider it reasonable to bump at the very least the minor version of the gem.
  - This is it's own commit so you can handle as you like.