v3.0.0-rc1

Pre-release for Webster 3.0:

• Introduce new API
• Improve performance
• Reorganize source code
• Change architecture to allow new protocols in the future (e.g. HTTP/2)

Amalgamation files:

• webster.hh and webster.cc for standard version with socket network implementation;
• webster.hh and webster-no-socket.cc for minimal version with no network implementation (you will need to provide one);