Modify boilerplate README created by Github.
Initial Haskell style guide.

Based on tibbe's guide, the GHC style guide, and other sources.
Use 2 spaces for indentation, not 4.
Remove 2 blank lines after import requirement.
Switch to Github style of block code.

This allows syntax highlighting according to language.
Remove alternative if-then-else alignment in monadic code.

This is no longer necessary in Haskell'2010.
Make examples consistent with new 2-indent rule.