Several XML-RPC functions are not implemented yet

[heryandi]

Several of the functions described in http://wiki.python.org/moin/PyPIXmlRpc are not implemented yet.

The un-implemented search(spec[, operator]) function in particular causes pip search <query> command to fail.

[heryandi]

I implemented the search function partially, just enough to make pip search works in 53af3b0.

Definitely not the complete implementation of the search API, but better than nothing :)