Update actionButton and FileInput

The bootstrap framework uses predefined classes allowing UI elements to be styled.  This actionButton input element allows the user to specify a style class from the bootstrap style set.  In addition to colors, this actionButton has options for size, icons, and block width.  Icons can come from the Font Awesome collection included in base shiny or from the glyphicons set included in Bootstrap 2.  This input element was adapted from the actionButton input available in the ShinySky project (http://www.github.com/analytixware/ShinySky).

![shiny actionbutton](https://cloud.githubusercontent.com/assets/7862984/4479984/4b6e5dbc-4993-11e4-9beb-0392cecdda10.PNG)

When building apps that utilize these actionButtons, the default styling of the fileInput buttons do not match (and are variable across browsers).  Several approaches exist for styling file input buttons.  This fileInput generates a normal button (that can be styled) and hides the actual input element.  This fileInput also allows the user to define the style class of the file upload progress bar.  By default the progress bar style is set to match the browse button. 

Default:
![shiny fileinput](https://cloud.githubusercontent.com/assets/7862984/4480036/c53c8056-4993-11e4-9fd7-6d47c0a5a9cd.PNG)

Info:
![shiny fileinput info](https://cloud.githubusercontent.com/assets/7862984/4480098/45d1a3b8-4994-11e4-9a3a-7f1f9dfdba58.PNG)

Danger:
![shiny fileinput danger](https://cloud.githubusercontent.com/assets/7862984/4480100/495a53ea-4994-11e4-807a-a55b883b8188.PNG)

Primary Button with Success Progress Bar:
![shiny fileinput combo](https://cloud.githubusercontent.com/assets/7862984/4480142/abc2f456-4994-11e4-8578-60a27fa4f8f5.PNG)