Edx/brianhw/include egginfo in packages

In order for packages that make use of entry points to work on a 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.

For example, it will include the egg-info for the luigi package.  With debug logging enabled, it will include:

```
DEBUG Adding package metadata to archive for "luigi" found at "<virtualenv-path>/lib/python2.7/site-packages/luigi-1.0.16-py2.7.egg-info"
DEBUG adding to tar: <virtualenv-path>/lib/python2.7/site-packages/luigi-1.0.16-py2.7.egg-info/installed-files.txt -> luigi-1.0.16-py2.7.egg-info/installed-files.txt
DEBUG adding to tar: <virtualenv-path>/lib/python2.7/site-packages/luigi-1.0.16-py2.7.egg-info/PKG-INFO -> luigi-1.0.16-py2.7.egg-info/PKG-INFO
DEBUG adding to tar: <virtualenv-path>/lib/python2.7/site-packages/luigi-1.0.16-py2.7.egg-info/SOURCES.txt -> luigi-1.0.16-py2.7.egg-info/SOURCES.txt
DEBUG adding to tar: <virtualenv-path>/lib/python2.7/site-packages/luigi-1.0.16-py2.7.egg-info/top_level.txt -> luigi-1.0.16-py2.7.egg-info/top_level.txt
DEBUG adding to tar: <virtualenv-path>/lib/python2.7/site-packages/luigi-1.0.16-py2.7.egg-info/dependency_links.txt -> luigi-1.0.16-py2.7.egg-info/dependency_links.txt
```