Travis CI support

Please note this commit uses a build image pointing to the fork http://github.com/ably-forks/active_hash.  This should be updated.
Prevent Rails 4 for < Ruby 1.9.3
JRuby CI support
Ruby 1.8 support bug fixes for new Aliases module and Enum spec
Ruby < 1.9.3 support bug fixes for buggy Sych YAML engine

Aliases for floats are treated as strings in the Sych YAML engine.  We ignore this bug because fixing this is out of the scope of this Gem
JRuby support bug fixes

Fixes error:

Failure/Error: country = Country.create
     ActiveRecord::StatementInvalid:
       ActiveRecord::JDBCError: [SQLITE_ERROR] SQL error or missing database (near "DEFAULT": syntax error): INSERT INTO "countries" VALUES(DEFAULT)
     # ./spec/associations/associations_spec.rb:172:in `(root)'
Ruby 2.0 support in CI, requires Rails 3+
Rubinius support bug fixes

Fix error (mismatch of error description):

2) ActiveHash Base custom finders find_by_<field_one>_and_<field_two>! for fields the class doesn't have raises a NoMethodError
     Failure/Error: lambda {
       expected NoMethodError with "undefined method `find_by_name_and_shoe_size!' for Country:Class", got #<NoMethodError: undefined method `find_by_name_and_shoe_size!' on Country (Class)>
Rails 4 support for Ruby 1.9.3+ in CI
JRuby and Rails 4 workaround for JDBC adapter bug

See https://github.com/jruby/activerecord-jdbc-adapter/issues/419
Until Rails 4 works with JRuby, this has to be disabled in CI