SpriteInfo: Design + refactor pass
* Updated SVG icons
* Added tab indexes, related #88. Still no tab on radio buttons
* Removed outline on dropdown focus
* Radio icons: fixed redirecting issue, using `div` instead of `a`. Temporary, until radio buttons. Related #156
* All icons: unselectable to prevent highlighting. Radio icons clickable
* SpriteSelector: fixed bottom padding in scroll wrapper

* Design pass on libraries to make sprites look more like they do in the SpriteSelector. Fixed scrolling overflow when reaching the bottom
* Started a colors variables file
* Added a light transform on sprite item hover

Related #12

* WIP: drag states in stage component

* WIP: Hacky drag canvas

* Update sprite position on drag

Use VM to put sprite into drag state and update the sprite's position while dragging.

Temporarily don't use the drawable data to drag a new canvas, this can happen whne we have somewhere to drag the sprite to.

Wire sprite info panel to VM

These aren't necessary to update in realtime, so throttle them to once every 30ms

Refactor sprite info behavior into a container and let it handle the raw events.

TODO: refactor again into redux

Very crude, requires a refactor to allow toggling

For the time being, update the position onChange. Eventually this will update onBlur/on "enter" key

Remove unused onNewCostumeClick prop

Fix no-var warnings

Move letters / numbers to top of the sprite library

* Remove errant conditional logic for backdrop / costume modal. Resolves GH-100
* Remove unused var. Re GH-100

* Stage/Backdrop: design pass. Changed how selected state works to keep width of pane from shifting. Switched to fixed pixel width to match design spec
* SpriteSelector: removed flex basis width. Pane grows to expand the empty space, since Stage is now fixed width
* SpriteInfo: updated to correct dropdown values. Updated 2nd row type sizing and radio box border-radius
* SpriteInfo: made labels non-selectable. StageArea: added border
* SpriteSelectorItem: Updating type size to match SpriteInfo

Filter toolbox to blocks available to the VM

Resolves #16

Update autoprefixer to the latest version 

https://greenkeeper.io/

Configurable SpriteSelectorItems per row (#90). Standardized spacer variable (#84). MenuBar Pass (#130)

* Standardized use of space units where appropriate
* Reversed box classes for easier readability in Inspector
* Sprite Area: removed unused info button
* SpriteSelectorItems: fixed spacing between rows. Isolated layout + component CSS, now reusable in other context. Items per row is now easily configurable
* MenuBar: refactored structure for clickable items

Update autoprefixer to the latest version 

Update postcss-loader to the latest version 

https://greenkeeper.io/

Update react-style-proptype to the latest version 

https://greenkeeper.io/

* Remove unnecessary dev dependencies

* Use large range on true "dev" dependencies

The exact versions of these dependencies are not important for building, so give them large ranges in order to quiet down greenkeeper.

I did not split them between dependencies and devDependencies because a package's dependencies are installed whenever the package is installed as a dependency. Installing all of these would be obnoxious and unnecessary.

Update eslint to the latest version 

https://greenkeeper.io/

https://greenkeeper.io/

Using postcss-modules-values with imported values failed on our current basic usage; it is apparently not mature enough to be used yet.

The syntax used by postcss-simple-vars is already familiar to most people familiar with modern CSS build systems.

chore(package): update autoprefixer to version 6.7.4

Update xhr to the latest version