Added shiva.indexer.CacheManager class
Added shiva.lastfm.LastFM class

This class is a wrapper around the pylast lib, which encapsulates the library's
logic and adds caching.
Replaced --low-ram flag with --write-every

In this big commit the --low-ram flag gets replaced with --write-every, which
receives a number. If that number is 1, no cache will be used, otherwise it's
used to write down to disk and clear RAM cache after that many tracks are
indexed.
Documentation for the --write-every parameter
New indexer structure

The indexer is now a module of its own.
CacheManager stripped out of the indexer

Now it's in an independent file.
CacheManager test
Moving indexer tests to integration dir
Fix to indexer integration tests
Added unit tests for the indexer
Ridiculously big timeout for python-dateutil
Install unittest2 only on python 2.6
Fixes to LastFM class
Added tests for shiva.indexer.lastfm
Merge pull request #99 from tooxie/cachemanager

CacheManager class