don't import catcher in setup.py

This is preventing `python-catcher` (and any other lib that depends on it, e.g., `ajenti`) from being installed.

Repro:
```bash
> virtualenv env
> source env/bin/activate
> pip install python-catcher
```

Once this (or some alternative change goes in), **the PyPI package should be updated ASAP**, since this is preventing people from installing dependents of `python-catcher` (e.g., `pip install ajenti` from a fresh python env).