Updates for running inside GHCi

Continuing from [this issue](https://github.com/yesodweb/yesod/pull/752), adds these two files:

* Configure the right indentation for Haskell mode (default Yesod scaffold is 4 spaces) and Hamlet mode.
* Use GHCi for project reloading.

I've also used this module on GHC 7.4, 7.6 and 7.8, there's nothing special in it.

@gregwebs might be interested in this as he played around with this approach a couple months back.

I've audaciously added `-DDEVELOPMENT` to the `.ghci` file. It could be argued that only GHCi dinosaurs like me still use .ghci files anymore, and rather `cabal repl` will properly set the right flags according to a properly configured Cabal file (via `cabal configure -fdev`). But if that's the case it can't hurt to add it (as these days `.ghci` files aren't even activated unless you `chmod 600` them). Feel free to disregard that patch if it doesn't fit. At any rate, I've documented in the `DevelMain` module that this is a handy setting to have on.