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)
```
5a54c99e98