Remove support for old Hixie protocols.
Hybi protocols 7 and 8 are still supported, in addition to
protocol 13 -  RFC 6455.
Update to version 0.4.0

*** IMPORTANT NOTE ***

This is the last minor version to support the Hixie protocol. I may do
bug fixes (e.g. 0.4.1) but 0.5.0 will drop the Hixie protocol support.
The latest released version of all major browsers (and web-socket-js)
support the IETF 6455 protocol.

- Other changes: updating TODO and release process notes.
Update to version 0.4.1

*** IMPORTANT NOTE ***

0.4.X is the last minor version to support the Hixie protocol. 0.5.0
will drop the Hixie protocol support. The latest released version of
all major browsers (and web-socket-js) support the IETF 6455 protocol.

- Other changes: add 'include/' sub-dir to source distribution and to
  installed packaged.
Merge pull request #70 from astrand/master

Remove support for old Hixie protocols
README: no longer supporting Hixie.

NOTE: Hixie support is in version 0.4.X. If necessary, I will branch
and apply critical fixes release a new 0.4.X tagged version.