Merge pull request #14 from zenoss/develop

Addition of keytab parameter
Merge pull request #17 from zenoss/develop

Pull in login error update
Merge pull request #19 from zenoss/develop

Look message parsing.
Merge pull request #21 from zenoss/develop

Exception raised to caller pull
Get auth key for header on kerberos logins.
Working kerberos method. Only doing auth at this point.
Check to see if krb5-workstation is installed.
Merge pull request #22 from zenoss/feature/kerberos

Feature/kerberos