handling auto-indent

There are two extra features related to auto-indentation that Parinfer users are starting to expect. Parinfer may grow in scope to handle these cases somehow, or we will have to detail how this can be handled external to it:

1. position of cursor after pressing enter (auto-indentation of newlines)
2. auto-indenting a region of text according to specific rules (realigning according to conventions)

Specifically, @snoe and @SevereOverfl0w expect the following from item 1: when pressing enter at the end of the last line:

(defn foo [a b]
  (let [x (+ a b)]
    x))|

They expect the cursor to be at the following position:

(defn foo [a b]
  (let [x (+ a b)]
    x))
   |

This behavior is handled in vim by using a mode called autoindent (seen here), which trivially copies the indentation of the previous line.

The behavior for item 2 can be handled by vim-clojure-static, which defines configurable rules for how to indent forms.

These two modes conflict with each other inside vim, so a solution to this problem must combine them when appropriate.