Changed the model's implementation: cleaner, better string repr.

The Models now no longer face the problem as in: http://effbot.org/zone/default-values.htm
They now have an repr (not str) method, and so have a much better representation.

Now compatible with Python's ast module (AFAIK)
Small Fixup in the previous commit
Corrected the names!

There was a regex mistake, fixed. Now the classes are named the same as before. Fixed inheritance. Someone start work on #11 now..
Corrected the names!

There was a regex mistake, fixed. Now the classes are named the same as before. Fixed inheritance. Someone start work on #11 now..
Merge http://github.com/pradyun/plyj
fix search&replace errors