Provide a static factory method to get client instance. Tighten up instantiation.
Introduce candidate version validation.
Rename default api constant and make it final.
Adds new endpoint to test if api is alive.
Introduce endpoint for determining default version for a candidate.
Advertise GvmClientException thrown on each API method.
Clean up calls using rest client, centralise exception handling.
Bump version to 0.5.0
Add Apache 2.0 license!
Up version to 0.5.1