restest 2.1.0

Release notes

• ADD: every request now returns the response size
• ADD: 'skip' attribute. If set to true, the request is skipped
• ADD: new action 'sleep' to wait for a number of milliseconds
• ADD: new 'NOT_EXISTS' / 'NOT_EXIST' condition
• ADD: new special field 'rt:size' to test against the response size
• ADD: --auth-mode option to set the default auth mode (auth or no)
• ENH: better error reporting on corner cases
• ENH: command line options are now sorted in --help
• FIX: fixed a bug that prevented the fields field as a one element list to be expanded correctly