This change updates the underlying type of VagrantCloudErrors.Errors to match the expected errors response type and adds a simple test to verify the parsing of various error responses.
Tests before change
```
--- FAIL: TestVagranCloudErrors (0.00s)
client_test.go:23: failed to decode error response: json: cannot unmarshal array into Go struct field VagrantCloudErrors.errors of type map[string][]string
client_test.go:23: failed to decode error response: json: cannot unmarshal array into Go struct field VagrantCloudErrors.errors of type map[string][]string
client_test.go:26: failed to get expected response; expected "", got "error1. error2"
client_test.go:23: failed to decode error response: json: cannot unmarshal array into Go struct field VagrantCloudErrors.errors of type map[string][]string
client_test.go:26: failed to get expected response; expected "", got "message Bad credentials"
```
Test after change
```
--- PASS: TestVagranCloudErrors (0.00s)
```
* stoped using url to pass the auth token and put it in the headers
* added newRequest method to VagrantCloudClient that sets json and auth headesr
* made VagrantCloudClient method pointers to avoid copies
Fixes the following vet reports:
post-processor/vagrant-cloud/client.go:81: arg resp for printf verb %s of wrong type: *net/http.Response
post-processor/vagrant-cloud/client.go:99: arg resp for printf verb %s of wrong type: *net/http.Response
post-processor/vagrant-cloud/client.go:131: arg resp for printf verb %s of wrong type: *net/http.Response
post-processor/vagrant-cloud/client.go:156: arg resp for printf verb %s of wrong type: *net/http.Response
post-processor/vagrant-cloud/client.go:175: arg resp for printf verb %s of wrong type: *net/http.Response
nywilken
Brian Fox
Davi Vidal
Megan Marsh
Adrien Delorme
Matthew Hooker
Emil Hessman
Jack Pearkes