Show when a new version of an existing package is installed

[billallen256]

If a user installs something like requests, but then later installs an older version of requests, then no message is displayed.

ipydeps.pip('requests')
New packages installed: requests

Later

ipydeps.pip('requests==0.0.1')
No new packages installed

This is because ipydeps discards version information when it uses pip freeze to get the the old and new lists of installed packages.