Displays info about [un]installed versions

[msabramo]

This is a variation on #2207 that doesn't write the output in package_name==version format, because @dstufft had some reservations about using that format and then people getting accustomed to it.

Displays version when installing and uninstalling -- e.g.:

Successfully installed pyrepl-0.8.4 pytest-2.6.4

and:

Uninstalling pyrepl-0.8.4:
  Successfully uninstalled pyrepl-0.8.4
Uninstalling pytest-2.6.4:
  Successfully uninstalled pytest-2.6.4

[msabramo]

Cc: @dstufft, @pfmoore

[msabramo]

Also see #2219 which does same for uninstall

[qwcode]

in #2219, you're logging the representation of the pkg_resources Distribution object.

for consistency, couldn't you do just do that here?

i.e. query for the installed distribution using pkg_resources.get_distribution and log that.

[msabramo]

@qwcode: Yeah, quite possibly. Thanks! Running tests locally now...

[msabramo]

Tests failed.

Anyway, @qwcode made good points over at #2219 (comment) so I think I'll make both uninstall and install use similar (explicit) code and do it one PR.

[msabramo]

@dstufft, @pfmoore, @qwcode: This now adds the version to put for both install and uninstall. For both it separates the name and version with a hyphen. I purposely didn't use == because @dstufft had concerns that people might come to rely on it and be annoyed if we decided to remove it.

[pfmoore]

👍