Create keyframe model to encapsulate general Skrollr logic, and subclass to start/target/end keyframes to create defaults for Flms-style animations.  Add supporting tests and migrations.  Build out UI for new/edit of image layers with keyframe attributes.
Remove debugger from gemfile; remove scroll_start initializer values in target and end keyframe models.
Remove slide stuff from keyframe model.
Use ||= instead of unless ... in build_default_keyframes
Fix indentation in image_layers_controller_spec
Minor formatting and variable name cleanups in tests
Add ability for user to specify layer position in start and end state using friendly position names; handle translation to CSS x,y coordinates under the hood
Merge pull request #13 from dhawt/slide_transitions

Slide transitions