Add config options

* defaultTheme
* defaultSize (TODO)
* includedThemes
* excludedThemes

exclude will take out themes from include, and if include is blank, all themes are included, with
exclude removing from there as well.

If you exclude a theme, and then use it, the component will still render,
but will be transparent. The todo here is to use 'default', which probably
should always be included.
Add configuration to readme
v0.2.0