Changes

0.2.0

1. Adapt the new v3 protocol.
2. Implement correlation protocol.
3. Support batch segment report.
4. Fix wrong context carrier endpoint data.
5. Rocks: fixed wrong version of luarocks.
6. Remove first ref variable.
7. Uniform the SpanLayer type name.

0.1.0

1. Establish the LUA tracing core.
2. Add the tracer implementation based on Nginx OpenResty.