Use quotes consistently in Gemfile

Use quotes consistently in Gemfile

Use set data structure to speed up circular reference checks on large/deeply nested objects

Fixes Rake::RDocTask deprecation warnings from Rake 0.9.0

Fixes for Rake::GemPackageTask deprecation warnings from Rake 0.9.0

Removed deprecated ActionMailer API and related tests

Not loading file if PLATFORM not available. 

import to java_import. 

Using java_import instead of import. Need to do this with rake 0.9.0 #jruby

Redundant condition in compute_asset_host is redundant.

Prefer 'each' syntax instead of 'for in'

Properly reference yml alias nodes

Create the dummy app if there's no test_unit but there's a dummy_path

as per the last version of the yml specifications : http://www.yaml.org/spec/1.2/spec.html#* alias//

Fix gemspec of full or mountable engines

Fix 'warning: ambiguous first argument; put parentheses or even spaces'.