Fix several sprockets_better_errors dependency errors (Sprockets::Rails::Helper::DependencyError), for pngs missing dependency declaration in ui theme.

Asset depends on 'jquery-ui/ui-bg_flat_75_ffffff_40x100.png' to generate properly but has not declared the dependency
Please add: `//= depend_on_asset "jquery-ui/ui-bg_flat_75_ffffff_40x100.png"` to '/Users/lu/.rvm/gems/ruby-2.0.0-p353@shiftit_rails3.2.16/gems/jquery-ui-rails-4.1.0/app/assets/stylesheets/jquery.ui.theme.css.erb'
Set encoding in Rakefile to fix "\xC3" on US-ASCII error.

rake aborted!
"\xC3" on US-ASCII
/Users/lu/.rvm/gems/ruby-2.0.0-p0/gems/json-1.8.1/lib/json/common.rb:155:in `encode'
/Users/lu/.rvm/gems/ruby-2.0.0-p0/gems/json-1.8.1/lib/json/common.rb:155:in `initialize'
/Users/lu/.rvm/gems/ruby-2.0.0-p0/gems/json-1.8.1/lib/json/common.rb:155:in `new'
/Users/lu/.rvm/gems/ruby-2.0.0-p0/gems/json-1.8.1/lib/json/common.rb:155:in `parse'
/Users/lu/jquery-ui-rails/Rakefile:38:in `block in map_dependencies'
/Users/lu/jquery-ui-rails/Rakefile:37:in `each'
/Users/lu/jquery-ui-rails/Rakefile:37:in `map_dependencies'
/Users/lu/jquery-ui-rails/Rakefile:54:in `<top (required)>'
/Users/lu/.rvm/gems/ruby-2.0.0-p0/bin/ruby_noexec_wrapper:14:in `eval'
/Users/lu/.rvm/gems/ruby-2.0.0-p0/bin/ruby_noexec_wrapper:14:in `<main>'
Modify Rakefile to introduce dependency declarations for images.
Add automatically generated assets with dependency declarations.
Move function to the place where it should be.
Merge pull request #60 from luisalima/master

Fix missing dependency declarations (accused by sprockets_better_errors gem).