Tart up Features

I took a pass at rewording the features section, with the intended audience of someone who thus far in their programming career experienced nothing that would get them excited about any of the following:

* laziness
* referential transparency
* function composability
* correctness
* proofs
* category theory
* algebraic data types
* monads

Considering how many programmers only take an interest in these things *after* getting into Haskell, it seems prudent to presume newbies will not be excited about them.

Instead I focused on pain points found commonly in mainstream programming but not in Haskell.