Enable the selection of multiple torrents in one go

This is especially helpful because contacting the server many times in one go might get you grey-listed

Also features some readability improvements

The diff looks pretty heavy, but if you use `--ignore-space-change` you will see that it is not that drastic. I inverted some checks for readability. Like:

```python
if mags and len(mags) > 0:
    # A lot of code
else
    print "No results"
```
becomes
```python
if not mags or len(mags) == 0:
    print "No results"
    return

# A lot of code
```