v5.0.0

This is huge update! Many improvements, code restructuring and refactoring, including some bugfixes.

Attention! There are some backward incompatibilities. Please read Migrating.md for more info.

• Registered PRC now can receive 3 arguments (as described in WAMP spec)
• Fixed window scheme check before it's actually needed (issue #28)
• Updated to WAMP spec: requestIDs are in range (0 - Number.MAX_SAFE_INTEGER)
• Fixed error: null value in argList during rpc invocation (issue #29)
• Detailed docs about error handling during rpc processing (thanks to @samson84)
• Overall code refactoring and restructuring (thanks to @421p)
• Added docs about using custom serializers
• Removed standalone browser version from repo/package