README: node-posix is battle-hardened by now

Disabled until support for v0.11 is added.

Fixes https://github.com/melor/node-posix/issues/20

New call: posix.initgroups()

Bindings are attempted to be loaded from various possible
locations where they could be.

Removed the obsolete node.js 0.4 support and added node.js 0.9
and 0.11 to the travis CI configuration.

This release is tagged with a new major version number as
backward compatibility (with node.js v0.4) is broken.

Remove getdomainname and setdomainname as they are not POSIX.

Some system implement sethostname(char *...) instead of const char *.
Since, a passing in const char * will cause an error on those platforms
and passing a char * will not cause an error on any platform, prefer the
latter.

Use process.versions to establish the require() path

get/set host/domain name

This makes npm hopefully automatically use either node-gyp or
node-waf, whichever is the proper tool with the particular node
version.

Also added node v0.8 to the travis config.