Fix the admin build, show this error

  error  build/javascripts/admin.js
  couldn't find file 'jquery'
  /home/misc/.gem/ruby/gems/sprockets-2.12.1/lib/sprockets/context.rb:106:in `resolve'
  /home/misc/.gem/ruby/gems/sprockets-2.12.1/lib/sprockets/context.rb:146:in `require_asset'
  /home/misc/.gem/ruby/gems/sprockets-2.12.1/lib/sprockets/directive_processor.rb:217:in `process_require_directive'
  /home/misc/.gem/ruby/gems/sprockets-2.12.1/lib/sprockets/directive_processor.rb:167:in `block in process_directives'
  /home/misc/.gem/ruby/gems/sprockets-2.12.1/lib/sprockets/directive_processor.rb:165:in `each'
  /home/misc/.gem/ruby/gems/sprockets-2.12.1/lib/sprockets/directive_processor.rb:165:in `process_directives'
  /home/misc/.gem/ruby/gems/sprockets-2.12.1/lib/sprockets/directive_processor.rb:99:in `evaluate'

using proper path for the file fix it.
Merge pull request #169 from mscherer/master

Fix the admin build, show this error