Upgrade Recast to 0.4.8 to fix options.writeback bug.

Bug introduced by: https://github.com/benjamn/recast/commit/e913b22f8f
Bug fixed by: https://github.com/benjamn/recast/commit/170e18091e
Merge pull request #105 from benjamn/fix-options.writeback-bug

Upgrade Recast to 0.4.8 to fix options.writeback bug