Thanks to @xdhanz for the catch, and pull request
closes #84

We may want to start cutting things at some point - it looks more
complicated than it really is!

Added alpha releas comments, inc. do not distribute yet.

Added install notes for install.sh.

Before this commit, you'd have to manually insert the kernel module for
OVS or OF kernel modules, and you couldn't run one regression test with
all 3.

Now, these are kmod insert/remove is handled automatically.

Simplifies installation step

Now, to reference mininet files, use 'import mininet.mininet'.

PYTHONPATH mods are no longer required for installation.

Added retry() function for createLink to see if it helps (probably won't.)
Random edits to docs.

Network may now be used with custom controllers.
An example of doing this is in nox.py, which instantiates at TreeNet
using a custom Controller, NoxController, that runs nox_core rather
than the reference controller.