Simpler client connections

[noisyboiler]

in response to https://github.com/noisyboiler/wampy/issues/39

• adds connect to a Router by a URL
• adds Transport decision by URL protocol/scheme
• adds quick start connection details to README
• adds detailed connection details to ReadTheDocs
• adds simple Router representation for Sessions based on the given URL when a Router instance is not provided to a Client
• removes forgotten features of MessageHandler
• MessageTypeMap now maps to classes instead of strings
• adds test cases for URL handling
• minor tweaks to logging, layout and Exception handling

[noisyboiler]

@manatlan thanks for your advice.