[Review] Request from 'vlewin' @ 'SUSE/connect/review_140612_preparations_for_client_integration_testing'

Please review the following changes:
  * 25ae096 check API verion in response headers
  * 4774e28 add connect library steps
  * 2370f00 fix ApiError exception message
  * 3df836d test inclusion of response headers
  * 173ed03 set response headers
  * 749aa83 introduce SUSE::Connect::Api::VERSION and forward it in accept header
  * 69cb6b7 fix indentation
  * b0e50b0 add rake tasks for mounting/unmounting the remotfs