Updated vendor.yml for Rails project

Hi

I have updated vendor.yml file for Rails project. Linguist will ignore assets dir and will detect the language correctly.
I have updated test_blob.rb
I have tested linguist locally. Works great and now detects the language correctly (there are a lot of javascripts files in my assets folders and before this fix Linguist detected language as JavaScript, not Ruby)

Before commit I run test:
bundle exec rake test
# Running tests:
Finished tests in 26.923862s, 3.7885 tests/s, 218.0965 assertions/s.                                     
102 tests, 5872 assertions, 0 failures, 0 errors, 0 skips
ruby -v: ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-linux]

![linguist1](https://cloud.githubusercontent.com/assets/2852169/3699108/9ce96f74-13ce-11e4-8891-37c592a91ac9.JPG)

Thanks,
Siarhei Kavaliou