Fixes activerecord-hackery#379

Since polyamorous 1.1.0 [differs from 1.2.0](activerecord-hackery/polyamorous@ca95023) only by the version number and the README file, it's perfectly unacquired to simply change the dependency version.

Copied from [5bf84bd](activerecord-hackery/squeel@5bf84b) which is not on the master branch, so can't be referenced.

Author: Gordon McNaughton

squeel.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency 'activerecord', '>= 3.0'
   s.add_dependency 'activesupport', '>= 3.0'
-  s.add_dependency 'polyamorous', '~> 1.1.0'
+  s.add_dependency 'polyamorous', '~> 1.2.0'
   s.add_development_dependency 'rspec', '~> 2.6.0'
   s.add_development_dependency 'faker', '~> 0.9.5'
   s.add_development_dependency 'sqlite3', '~> 1.3.3'