Okta-jwt-verifier

- Verify claims before signature, issue 34

- Remove deprecation warning from IDTokenVerifier, add missing fix in v0.2.1

- Fix passing timeout parameter to cached session, issue 22
- Fix verify_expiration method, issue 24
- Remove deprecation warning from IDTokenVerifier and AccessTokenVerifier classes by separating JWTVerifier class

- Add classes IDTokenVerifier and AccessTokenVerifier
- Mark JWTVerifier class as deprecated. This class will be removed in the next major version.
- Add proxy support
- Update README
- Few codebase improvements

_New features:_
- Separate classes for verifying ID Tokens and Access Tokens
- Add proxy support

- Initial release