Find errors node when nested in response

[BradHudson]

We found a case where the errors node is nested within the response from the User Registration API. Originally we were only looking at the first level for the errors node, but this is deeper. The solution is we look at the first level for the errors node, but then look one level deeper for it. If the response is nil, we return blank as it originally did. Also did a little boyscouting in changing the old 'fail error' to the newer 'raise error'.

Staging: Uses a pregem version of the gem along with some changes I have in a C-M branch. http://m-car-ins.cbmtn.io/user/register

Response:

{"ResponseUserCreate"=>
  {"Request"=>
    {"DeveloperKey"=>"",
     "HostSite"=>"US",
     "Test"=>"False",
     "ExternalID"=>nil,
     "Email"=>"bradley.hudson@example.com",
     "Address1"=>nil,
     "Address2"=>nil,
     "Phone"=>nil,
     "LastLoginDT"=>nil,
     "Status"=>"active",
     "UserType"=>"jobseeker",
     "Gender"=>"U",
     "BirthDate"=>nil,
     "CobrandCode"=>nil,
     "WorkStatus"=>nil,
     "Ethnicity"=>nil,
     "SendEmail"=>"True",
     "City"=>nil,
     "State"=>nil,
     "PostalCode"=>nil,
     "CountryCode"=>"US",
     "FirstName"=>"Brad",
     "LastName"=>"Hudson",
     "CreatedDT"=>nil,
     "AllowNewsletterEmails"=>"True",
     "AllowEventEmails"=>"True",
     "AllowPartnerEmails"=>"True",
     "Domain"=>nil,
     "RegistrationPath"=>"RPMTN",
     "CustomValues"=>
      {"CustomValue"=>
        [{"Key"=>"SubscribeToJobRecs", "Value"=>"true"},
         {"Key"=>"SubscribeToAVN", "Value"=>"true"},
         {"Key"=>"SubscribeToRVN", "Value"=>"true"}]}},
   "Errors"=>{"Error"=>"City requires a value"},
   "TimeResponseSent"=>"12/21/2016 9:42:47 AM",
   "TimeElapsed"=>"0.0156",
   "Status"=>"Fail",
   "ResponseExternalID"=>nil}}