properly initialize LogSubscriber object, fixes problem with Rails 4.1.4
add rails4.1 test stub and tests
Bump version to 4.0.50 and update CHANGELOG

[ci:skip]
Introduce an assertion macro for checking expected values, and include bug check messages in crash reports.
Introduce ServerKit, MemoryKit and some new data structures
Continue working on ServerKit.
Continue working on ServerKit.
Various ServerKit optimizations

- Reduce number of reference count manipulations in FileBufferedChannel
- Use raw system calls instead of OXT wrappers. This reduces the number
  of atomic operations
- Reorder some code for better cache locality
Update Channel documentation and add unit tests for it
Add unit tests for LString
Add unit tests for mbuf
Add unit tests for HeaderTable
Allow Channel data callbacks to end consumption prematurely
Allow Channel to report back the number of bytes its data callback has consumed
Implement FileBufferedChannel::feedError
Make HttpServer work with the recent Channel changes, and implement support for request bodies
Rename FdChannel to FdInputChannel
Add unit tests for ServerKit::Server and improve its documentation
Improve ServerKit::BaseServer logging
Fix a bug in Channel