Introduction of Runtime.js

Here is a list of whats in this commit (sorry for the big commit):
 - Introduced `Runtime.js` as a core abstraction around which different frameworks can plug into glimpse
 - Shifted `glimpseExpress.js` into its own `express` folder and renamed to `express/index.js` (in preparation for pushing it out to its own module eventually)
 - Pulled the tab implementation of `ReqRes` out of `glimpseExpress.js` into its own tab `express/tabs/requestResponse.js`
 - Pulled the script injection logic out of `glimpseExpress.js` and put it into its own provider `scriptInjector.js`
 - Introduced `configuration.js` as a means by which tabs, etc can be registered