Build failure on node 0.8+

When trying to build node-cas-sfu on node 0.8+, I was seeing a build failure (copied below). According to https://github.com/astro/node-expat/issues/39, node-expat@1.4.1 has build issues on node 0.8, which switching to use node-gyp instead of waf solves. Upgrading node-cas-sfu to use xml2json@1.3.2 instead of 1.2.x solves the problem.

```
Checking for program g++ or c++          : /usr/bin/g++ 
Checking for program cpp                 : /usr/bin/cpp 
Checking for program ar                  : /usr/bin/ar 
Checking for program ranlib              : /usr/bin/ranlib 
Checking for g++                         : ok  
Checking for node path                   : not found 
Checking for node prefix                 : ok /usr/local 
Checking for header expat.h              : not installed 
/opt/Hilary/node_modules/cas-sfu/node_modules/xml2json/node_modules/node-expat/wscript:13: error: the configuration failed (see '/opt/Hilary/node_modules/cas-sfu/node_modules/xml2json/node_modules/node-expat/build/config.log')
npm info node-expat@1.4.1 Failed to exec install script
npm info /opt/Hilary/node_modules/cas-sfu/node_modules/xml2json/node_modules/node-expat unbuild
npm info preuninstall node-expat@1.4.1
npm info uninstall node-expat@1.4.1
npm info postuninstall node-expat@1.4.1
npm info /opt/Hilary/node_modules/cas-sfu/node_modules/xml2json unbuild
npm info preuninstall xml2json@0.2.4
npm info uninstall xml2json@0.2.4
npm info postuninstall xml2json@0.2.4
npm info /opt/Hilary/node_modules/cas-sfu unbuild
npm info preuninstall cas-sfu@1.0.5
npm info uninstall cas-sfu@1.0.5
npm info postuninstall cas-sfu@1.0.5
npm ERR! 
npm ERR! Additional logging details can be found in:
npm ERR!     /opt/Hilary/npm-debug.log
npm ERR! not ok code 0
```