Added styling to spotify-objects and voting-objects

Objects themselves match prototype (minus buttons), but they still all
render one after another
Added animation-timing-function mixin
Updated look of "add" section

Still no interactivity—no way to cycle between search results
Added mixins and replaced old properties

Added transition, border-radius, box-shadow, and filter mixins
Moved CSS rule defining imports after main definitions
Fixed bug with transition mixin
Added some flex-box mixins
Adjusted filter settings on background

Performance concerns
Stopped animating the add section's background
Brought in velocity.js and hammer.js
Added setPrefixedStyle function to util
Added comments to old util functions
Changed global background color to black
Added swiping and panning to search results
Fixed setPrefixedStyle
Changed add for voting button's loading gif
Cleaned up Spotify object copy
Replaced velocity call with call to util.setPrefixedStyle
Cleaned animation, cleared add page after adding track
Removed search-results styling