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
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Move smartparens pair definition out of hooks