Grid node recognition

# Additions:
+ Functionality has been added, that will allow a local user to call `BrowserInstallation.isGoogleChromeInstalled()` statically

+ User is able to now call `BrowserInstallation.get*InstallationBinary()` to fetch the full-path of the browser's binary (useful if multiple installations are present, and you are unsure where it's fetching

## Grid / Node
+ Node now passes configurations to the hub which tell the grid if the node has particular browsers installed.  

![screen shot 2014-04-21 at 14 59 55](https://cloud.githubusercontent.com/assets/2972876/2757790/2af12d66-c988-11e3-9f14-1bce3f1140b5.png)

(*the icons will have red `x`'s through them, and when hovering, will state `"browser not available"`.)