Preliminary commit for browserify compatibility

This is the first stage of my commits for issue #609 that will make the
npm module browserify friendly and browser friendly.

The grunt-browserify module has been introduced to replace
grunt-contrib-concat. Browserify automatically concatenates files and so
there is no need for a concat step.

The faye-websocket module was problematic so I moved the require out to
a separate module within the lib directory. The websocket module is a
folder containing a package.json, directing library consumers to the
entry point that is appropriate for their environment. Browserify picks
browser.js (which simply returns an object holding window.WebSocket)
while everyone else gets the faye-websocket module.

In addition, as browserify handles all the requires, there's no need to
detect the environment or include any pre-built modules. I've removed
the pre-built when and faye-websocket files in favour of letting
browserify use the modules within node_modules. This should make it
easier to maintain dependencies in future versions of this library.

One side effect of this browserify compatibility is that, in order to
allow the library to be globally available in the browser as `Mopidy`,
I've had to set Mopidy as the exported object instead of as a key of the
exported object. To elaborate further, the current API would be like the
following:

    var Mopidy = require('mopidy').Mopidy;

However, with this change, the API would be like this:

    var Mopidy = require('mopidy');

I'm not sure whether this would be an issue and so I think it's worth
discussing further. It's possible that node developers won't have a
problem but, if they did, a potential workaround within the mopidy.js
file would be:

   Mopidy.Mopidy = Mopidy;

This would allow developers to choose either of the following:

    var Mopidy = require('mopidy');
    var Mopidy = require('mopidy').Mopidy;

Could be a little odd to do this though

When testing the browserify build, I noticed a strange error thrown when
making the initial websocket connection. I managed to track it down to
an IE 'feature' that crops up when you alias in-built functions. In
particular, the when module was aliasing setImmediate to an internal
function (nextTick.) In a newer version of when, the function is
instead aliased to the browserify process.nextTick. This works well
because substack already had that covered.

With when@2.7.0, IE11 appears to be working well. IE10 is still pending
a test.
Update test so that it correctly requires the mopidy module

As part of issue #609, the require statement in mopidy-test.js should
have been updated as the API to require mopidy has changed from:

    require('mopidy').Mopidy;

to:

    require('mopidy');
Updated the test process for mopidy.js

Following on from the previous issue #609 commits, I have updated the
build process to cater to the fact that the files are no longer
available to test in the browser environment.

2 new browserify tasks build the mopidy.js file and then when.js file
(available in node_modules.) These files are placed in test/lib/ (This
directory has been added to the .gitignore file) prior to the running of
the buster tests. As these files are ignored in the .gitignore, this
will prevent them from being committed to git and also prevent them from
being packaged up to npm.

Once the tests have completed, the main browserify task will run to
build the official browser release.
Updated npm version to 0.2.0

After using this in our live mopidy system for the last 2 weeks, I am
quite happy about the stability of the release. I've updated the
package.json file as it makes sense to incorporate this in to my final
commit for issue #609
Merge remote-tracking branch 'connrs/browserify' into develop

Conflicts:
	js/Gruntfile.js
js: Update Node instructions, add changelog
js: Update all dependencies
js: Build updated mopidy.js