1.9.2 compatibility fix: don't try to use ruby-debug on 1.9.2.
1.9.2 compatibility fix: don't try to use ruby-debug on 1.9.2.

On 1.9.2, I'm getting errors like these:

dyld: lazy symbol binding failed: Symbol not found: _rb_method_node
  Referenced from: /Users/mmarston/.rvm/gems/ruby-1.9.2-p0/gems/ruby-debug-base19-0.11.23/lib/ruby_debug.bundle
  Expected in: flat namespace

dyld: Symbol not found: _rb_method_node
  Referenced from: /Users/mmarston/.rvm/gems/ruby-1.9.2-p0/gems/ruby-debug-base19-0.11.23/lib/ruby_debug.bundle
  Expected in: flat namespace

Shopify/vcr,ZmagoD/vcr,nishanbose/vcr,cemo/vcr,davidbebb/vcr,Shopify/vcr,chriswoodrich/vcr,asymmetric/vcr,chriswoodrich/vcr,intfrr/vcr,irfanah/vcr,myronmarston/vcr,nishanbose/vcr,intfrr/vcr,benjaminoakes/vcr,mcfiredrill/vcr,cemo/vcr,ihassin/vcr,ZmagoD/vcr,davidbebb/vcr,travis-repos/vcr,mcfiredrill/vcr,allyapp/vcr,ihassin/vcr,asymmetric/vcr,allyapp/vcr,irfanah/vcr,myronmarston/vcr