* 3.0.0 - Nov 19 2015
- Instead of returning a dictionary from CreateEnv, return a new
VirtualEnvInfo object. This is backwards-compatible, as it implements
__getitem__ and __setitem__ with the fields and thus can be used the same.
- Add methods ensureImport and ensureImportGlobal (that work on a given
virtualenv directory, or the global one created by enableOnDemandImporter,
respectively). These can be used when the package name does not match the
module name (like "biopython" package provides "Bio"), instead of creating a
new virtualenv for each instance, and for appending to existing envs to
prevent number that would be stacked under normal usage.

* 2.1.0 - Nov 18 2015
- For auto-generated temporary requirements.txt file, use the virtualenv directory instead of parent temp directory to keep things cleaner and isolated
- Allow specifying a temporary directory on the enableOnDemandImporter call.

* 2.0.1 - Nov 17 2015
- Split up module into a couple files
- Split out the package installation from env creation, to support adding to
existing envs
- Add support for enabling automatically trying to install modules after
failed import, by calling "VirtualEnvOnDemand.enableOnDemandImporter()"
- Update docs accordingly
