Drop "indent" option

This seemed like a good idea but I have yet to use it, plus it's of
questionable value without a corresponding way to set 'expandtab'.
Ask dispatch.vim for compiler if available
Document automatic shell escaping

This is the preferred interface going forwards, as it seems way cleaner
than the alternative of including a shellescape transformation.
Auto cd on :make

This only happens if

* A list of arguments was used.
* None of those arguments contains the project root.
* Our errorformat is in effect.

This is a more than a bit kludgy, and I recommend explicitly passing in
the project root if you can.