Use paredit-check-region-for-delete.

paredit-check-region-for-delete was added in v23 and replaces -evil-check-region.
Map 'X' to paredit-backward-delete
Don't break compatibility with paredit 22.

Adds a check to see if the function paredit-check-region-state is
defined.  If it is we will rely on the old behavior.
Merge pull request #4 from Expez/paredit-23

Update evil-paredit to use paredit v23 instead of v22.
Merge pull request #5 from Expez/add-binding

Map 'X' to paredit-backward-delete