Fix shift/reduce conflicts

``` shell
code/reactive_record(master)✓ rake
racc -l -o lib/parser.rb lib/parser.y
9 shift/reduce conflicts
/Users/chris/.rvm/rubies/ruby-1.9.3-p448/bin/ruby -S rspec ./spec/lexer_spec.rb ./spec/parser_spec.rb ./spec/reactive_record_spec.rb
........................

Finished in 0.45743 seconds
24 examples, 0 failures
```
