Closes #84: Globally enable $http cache for CartoAPIService

This seems to remove most of the sluggishness of the app.
Best guess is that we were sending too many requests from
a single IP and getting throttled. With the cache in place
the app seems to function as normal and quite a bit snappier.
Add overlay loading div when transitioning map > compare|detail

If the transition to detail or compare takes more than overlayTriggerMillis
then overlay the loading spinner. This should probably be styled further.

I was only able to get this overlay to appear a few times after
enabling the $http cache option in the previous commit.
Closes #79: Animate bar chart up instead of down
Updated Navbar

-navbar minimizes on scroll and remains minimized(hiding icons)
Thin out axis and customize labels
Move controls out to separate directive and group barcharts under it
Logarithmic binning for sq ft graph; style updates
Merge pull request #99 from CloudNiner/feature/investigate-transition-slow

Feature/investigate transition slow
Merge pull request #100 from CloudNiner/feature/barchart-animate-down

Closes #79: Animate bar chart up instead of down
Remove references to parent; include opacity difference
Merge pull request #101 from azavea/Navbar-Update

Updated Navbar
Clean up according to angular conventions
Merge pull request #76 from azavea/feature/barchart-label

Thin out axis and customize labels
Update README.md