Refactor TS build and fix testing

This change is largely just moving files with minor tweaks to them to fix,
the rest of the commit is build process changes:

- The addons/ and test/ dirs have been moved to src/
- The build directory has been removed
- TypeScript builds are output in out/, this is where tests are run
- The demo now relies on the dist/ build which is performed as part of ./bin/build
- Addons are now shipped under the ./build directory

src/test/addons/test.js

@@ -0,0 +1,10 @@
+var assert = require('chai').assert;
+var Terminal = require('../../xterm');
+
+describe('xterm.js addons', function() {
+  it('should load addons with Terminal.loadAddon', function () {
+    Terminal.loadAddon('attach');
+    // Test that addon was loaded successfully
+    assert.equal(typeof Terminal.prototype.attach, 'function');
+  });
+});