SeafConnection: consistently handle HttpRequestException
Always check for SSLHandshakeException, by using private method
to check which HttpRequestException occured, and return
corresponding SeafException
SeafConnection: Let checkRequestResponseStatus handle various HTTP status
Extend checkRequestResponseStatus, so it can be used to handle other
http status codes than 200 as success.
SeafConnection: Use constants for connection and read timeouts
Merge pull request #74 from alfh/feature_consistent_logging_seafconnection

SeafConnection: Consistent handling of HttpRequestException