Add support for adding egg-info files to packages archive.

In order for packages that make use of entry points to work on Hadoop
node, the relevant egg-info directories also need to be copied to those
nodes. This change performs a simple check to see if a related egg-info
is present for a requested package, and adds those files as well.
Add test data for creating package archives with egg-info.
Merge pull request #454 from edx/edx/brianhw/include-egginfo-in-packages

Edx/brianhw/include egginfo in packages