Reworked env helper to support multiple export format
 * Change how env helper was made to support more env export format in
   the future.
 * Added support for autoenv format.
 * Added tests for script and autoenv formats.
Added missing require statements
Changed a bit user env command
 * The --script is deprecated in favor of a --format argument.
 * Added possibility to export to autoenv format directly.
Documented new autoenv export feature and bumped to 1.4.0.dev1
Merge branch 'feature-autoenv-export' into 1.x