Added some description to generate actionview gem [ci skip]
rake -> bin/rake
Merge pull request #11341 from arunagw/added-missing-actionview-to-install

Added description in actionview gemspec.
Merge pull request #11582 from steveklabnik/add_bin

rake -> bin/rake
used flat_map instead of map.flatten
Merge pull request #11598 from Karunakar/flat_map1

Used flat_map instead of map.flatten in mas_many_through_associations_test.rb
grab executable from rubygems