Move preview_js inline

Ensures that all controls registered upon customize_register action
are available when the postMessage JS is generated. Also this is
in-line with what is done for inline CSS.
Merge branch 'inline-js-preview' of github.com:x-team/wp-styles into x-team-inline-js-preview

Conflicts:
	classes/styles-customize.php
	classes/styles-plugin.php
Handle script dependencies for #24.
Merge pull request #24 from x-team/inline-js-preview

Move Customizer preview_js inline. Simplifies logic and makes it easier for plugins to add to customizer javascript.