Initial refactoring of API

- split into multiple files
- remove Sailthru redundancy
Rework exceptions

- Rename redundant exceptions
- Exceptions should subclass StandardError
- Depend on Ruby 2.1’s cause feature to track underlying exception
Use gemspec for deps where possible
Misc cleanup
Remove verify_ssl toggle
Extract constant
Remove deprecated “send” method
General cleanup
More rakefile cleanup, use Bundler’s gem tasks
Add easy credentials initialization for Rails apps
liney mclinebreaks
move rake into gemspec
merge master
More cleanup
Remove lockfile
merge latest
Undo this
Rdoc
Tidying up: Remove double-empty lines
Revert "Remove verify_ssl toggle"

This reverts commit a045943471a758f12e947ad6146297eb6e3d994f.