customizing templates and bootstrap

I have added supports of customized themes and bootstrap files, which enable me to use bootstrap 3 in my own package documentation: [http://rtalks.net/iterpc/](http://rtalks.net/iterpc/)

For those interested in bootstrap 3 theme, you can have a look of [here](https://github.com/randy3k/iterpc/tree/master/inst/staticdocs)

Screenshot:
![screen shot 2014-04-01 at 1 30 54 am](https://cloud.githubusercontent.com/assets/1690993/2576958/fd308f86-b977-11e3-8e7c-333458ffead0.png)