do not generate id method (was for 1.8 only)

see https://github.com/rails-api/active_model_serializers/issues/127
for original motivation
require ruby >= 1.9.2 in gemspec [ci skip]

* use consistent quotes
remove 1.8 versions from travis
add note to changelog [ci skip]
upgrade hash syntax
upgrade hash syntax in tests
add ruby 1.8 install note [ci skip]

fixes #310
require rails >= 3.2

* remove ancient confusing comment in SerializerGenerator
require ruby >= 1.9.3

* remove 1.9.2 from travis
Merge pull request #321 from teeparham/ruby19

Remove support for ruby 1.8 (fixes #310)