Making use of the closure-util package

This provides some initial development utilities for people using Node.

Instructions for installing:

    npm install

After pulling down the dependencies, you can start a developement server that provides the libraries (ol and Closure Library) in debug mode (not minified/compiled).  Run the dev server with the following:

    npm start

Currently, the example index page needs to be built with `build.py`.  After building that, you should be able to browse all static files, view the examples and run the tests.
Don't use private `date_` property (see #1026)

It looks like at some point the Closure Library exposed a public `date` property for this same purpose.  The version of the Closure Library that comes with the closure-util package uses this property.  At some point later, I'll demonstrate how we can control which version of the library we depend on.
Test conventions

 * use `be` or `equal` for strict equality tests
 * use `be.a` for `instanceof` checks
 * use dot instead of bracket notation
Better setup/teardown for ol.proj tests
WebGL image layer tests require the common proj
Unnecessary spy
Preemptively set global properties

As mentioned in the comments, calling goog.getUid and goog.events.listen on the global object (as done in map.js and deviceorientation.js) set global properties.  To let Mocha check for other leaks, we preemptively set these properties.
Merge pull request #1027 from tschaub/closure-util

Use the closure-util package.  Documentation will come when this is a more complete solution.  See #1027 for basic usage instructions.