Update the README file development section.
Update the README file development section.

Add more prerequisites to set up a local environment for development on
Ubuntu and the Fedora equivalents.

* libxml2 and libxslt are needed to build lxml.
* mysql libs are needed to build MySQL-python.

Change-Id: I4627b34ba72d677975c8c067e981fca732d78215

rdo-management/tuskar,rdo-management/tuskar,rdo-management/tuskar,tuskar/tuskar