Updating External Authentication to support new AwesomeSpawn 1.2.1 usage.

- Using the new AwesomeSpawn using symbols for
parameters, i.e. :fixed_primary instead of "--fixed-primary"
and eliminating the need for nil for options with no values.
Merge pull request #229 from abellotti/external_auth_awesomespawn

Updating External Authentication to support new AwesomeSpawn 1.2.1 usage...