(maint) Pin racc gem to 1.4.9

racc recently released 1.4.10, which has changes which break on Ruby
1.8.7

https://github.com/tenderlove/racc/commit/c43068f0886a339c95420fb41dd896ddee66d722
https://github.com/tenderlove/racc/issues/32
Merge branch 'stable'

* stable:
  (maint) Pin racc gem to 1.4.9