Add compileClient

[ForbesLindesay]

This needs testing, I haven't actually tried running this.

[RobLoach]

There aren't much docs for .compileClient, so I'm not quite sure what it accomplishes. Does it mimic that of Jade's http://jade-lang.com/api/ ? The .compile() implementation, returned as a string that can be used on the client side?

Know if test-transformer has support for it? For everything client-side, I've been using Browserify.

[ForbesLindesay]

It's intended to allow us to write a browserify transform that replaces code like:

var fnt = require('jstransformer')(require('jstransformer-function'));
var fn = fnt.compile('return "Hello" + this.name');

with:

var fn = function (locals) { return function () { return "Hello" + this.name }.call(this) };

Unfortunately, the output format isn't very standardised yet, so we need to think about what this should be. A few questions to answer:

• should it be a function expression (as above) or a function declaration (as what jade@2.0.0 generates by default).
• how should we handle runtime dependencies? We could require them to be inlined, or perhaps we should generate an ES6 or CommonJS module format?

We should answer those questions and then build tests for them. We don't really need to actually test in real browsers. compileClient really just means, compileToJavaScriptString, but client is a bit snappier and is the only real use case I can think of.