Add key bindings for godoc

C-h G -> godoc: can be used in any mode

C-h f -> godoc-at-point: go-mode only
Merge pull request #578 from dougm/go

Add help-command mapping for godoc
Move smartparens pair definition out of hooks

There are two reasons for doing this:
- It's inefficient, we don't have to define the pairs every time we
  enter the mode.
- It's extremely difficult to override the pair definition, even with
  `eval-after-load` and `add-hook`
Merge pull request #585 from toctan/smartparens

Move smartparens pair definition out of hooks
Look for Quicklisp in ~/quicklisp and ~/.quicklisp

In `prelude-common-lisp.el`, look in both `~/quicklisp/` and
`~/.quicklisp/` for `slime-helper.el`, on the assumption that most users
will have Quicklisp installed in one of these two locations.

This commit fixes #582
Merge pull request #587 from swhalen/two-quicklisp-dirs

Look for Quicklisp in ~/quicklisp and ~/.quicklisp