README: Running the app requires an HTTP reverse proxy

The "stb-tester-service" backend no longer supports CORS.
package.json: Sort dependencies alphabetically
make check: Run jshint static analyzer

Run `npm install` to install jshint.

The various configuration options are documented at
http://jshint.com/docs/options/

The `sed` in the makefile is to make jshint's output match the format of
gcc errors, `grep -n`, etc., so that my editor can navigate to the
location of each error.

The changes to app.js are to comply with jshint: Mostly adding missing
semicolons or removing unnecessary ones, using "!==" instead of "!="
(the latter does implicit typecasting), and wrapping overly long lines.