Merge pull request #25 from euanh/planexsc

Refactor build logic and fix more pylint warnings
build: Remove srpmutil

The native Python RPM library in CentOS 6.4 works so we don't need
srpmutil any more.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
build: Switch from deprecated md5 to hashlib

Signed-off-by: Euan Harris <euan.harris@citrix.com>
install: Remove demjson

Since Python 2.6, the standard library has included
a json module based on simplejson

Signed-off-by: Euan Harris <euan.harris@citrix.com>