Update ruby-parser to 3.1.3.

3.1.2 fixes temporary file creation.

=== 3.1.3 / 2013-04-09

* 2 bug fixes:

  * Fixed begin w/ else but no rescue. (whitequark)
  * Removed literal stripping from block_append. Not its job.

=== 3.1.2 / 2013-03-18

* 1 minor enhancement:

  * OMG A SECURITY ISSUE FOR CODE NOBODY USES... EVER

(taca)