Add #version_exists?
Refactor active_versions
Only return version url if version exists
Merge pull request #1099 from woodwardjd/maintain_file_conversion_across_processing

Maintain file type conversion across processing
Add sprockets rails helper info for Rails 4
Fix homepage in gemspec
Merge pull request #1106 from steveklabnik/patch-1

Fix homepage in gemspec
Drop multi_json in favor of vanilla json, closes #1105
Merge pull request #1092 from tmaier/master

Add method #version_exists?
Don't enforce the move_to_cache config option on versions, closes #1088
fix busted tests on ruby 1.8.7 (1.9.3 also re-checked)