General Improvements

- Adding StateEnumeration abstract class
- Adding CurlOptHelper abstract class to make curl opt reading easier
- Some updates to ICurlPlusContainer
- Some other minor cleanup
General Improvements

- Removing AbstractCurlPlusResponse because it was useless
- Removing CurlPlusFileResponse because it was useless
- Updating CurlOptHelper to....work
- Updating CurlPlusClientTest to have 100% code coverage over CurlPlusClient
Updating README.md