adding NPM dependency badge to readme

Uses the david-dm.org service.
add CodeClimate badge to readme

related to issue #440
Update Google Analytics tracking code to Universal Analytics.
Migrate event tracking to use analytics.js
a first attempt at merging in the back-end code from streetmix-be

This replaces the separate Restify app (https://github.com/codeforamerica/streetmix-be) and merges all its routes, models, and controllers into this Express app.
only load .env file if it exists
updating config for staging environment
preparing config for production as well
updating Apiary config file

... not that I'm sure if there's reason to use Apiary.
updating readme to reflect the merging of the two apps/repos
adding a missing environment variable to readme
removing out of date cronjob code

seemed to be removed from back-end: https://github.com/codeforamerica/streetmix-be/commit/b2052a0fb3d6c86f157114845335e3ad4c5641ff
production node should still log to console

PaperTrail seems to pick it up from there
fix URL for POST feedback endpoint

identified in https://github.com/codeforamerica/streetmix/pull/442#issuecomment-52730078
Change references to @streetmixapp to @streetmix
Restoring ragged line endings

They'd be nice to remove eventually, but leaving them in for now will make merges simpler.
Merge pull request #443 from codeforamerica/new-twitter-handle

Change references to @streetmixapp to @streetmix
fix for: feedback being sent an infinite number of times

reported by Lou: https://github.com/codeforamerica/streetmix/pull/442#issuecomment-53021781

Even though the feedback API endpoint returned a 202 HTTP status code, jQuery reported a failure. Seems to work when JSON is returned instead of a straight status string.
removing repeated imports
Change @streetmixapp to @streetmix twitter handle on scripts.js