added pip to make install

As suggested, I added pip to make install.

However, I'm not sure whether this is how we want this. Packages now go to /usr/lib/micropython instead of /.micropython/lib. I'm not fully sure what's going on with the virtualenvs in this script.
Please review thoroughly and bounce in case.

Somehow I also managed to get some commits into this from an earlier experiment that shouldn't be there at all.
Thanks for your patience, I still have a lot to learn.
Well, they both should be in sys.path, for example:
~~~~
['', '/home/pfalcon/.micropython/lib', '/usr/lib/micropython']
~~~~

/usr/lib/micropython is there to be ready for when distros will want to ship it (and they surely will want to install modules in system-wide location, easily reusable by different users on the system). But we're not yet there, so we should keep installing modules into ~/.micropython/lib because it's more convenient for developer user (one who will do "make install"), mpre secure (I personally wouldn't recommend anyone to run pip-micropython as root).