Clean up and improve the interactive console

This is #830 

With this branch you can do this:

```
In [3]: commands.check('-l')
Scanning posts....done!
[2014-04-18T01:39:49Z] ERROR: check: Error with: output/2014/index.html [Errno 2] No such file or directory: 'output/2014/index.html'
[2014-04-18T01:39:49Z] ERROR: check: Error with: output/archive.html [Errno 2] No such file or directory: 'output/archive.html'
[2014-04-18T01:39:49Z] ERROR: check: Error with: output/galleries/index.html [Errno 2] No such file or directory: 'output/galleries/index.html'
[2014-04-18T01:39:49Z] ERROR: check: Error with: output/index.html [Errno 2] No such file or directory: 'output/index.html'
[2014-04-18T01:39:49Z] ERROR: check: Error with: output/categories/index.html [Errno 2] No such file or directory: 'output/categories/index.html'
```

And even, if you know the magic parameters...

```
In [4]: commands.check(links=True)
Scanning posts....done!
[2014-04-18T01:39:59Z] ERROR: check: Error with: output/2014/index.html [Errno 2] No such file or directory: 'output/2014/index.html'
[2014-04-18T01:39:59Z] ERROR: check: Error with: output/archive.html [Errno 2] No such file or directory: 'output/archive.html'
[2014-04-18T01:39:59Z] ERROR: check: Error with: output/galleries/index.html [Errno 2] No such file or directory: 'output/galleries/index.html'
[2014-04-18T01:39:59Z] ERROR: check: Error with: output/index.html [Errno 2] No such file or directory: 'output/index.html'
[2014-04-18T01:39:59Z] ERROR: check: Error with: output/categories/index.html [Errno 2] No such file or directory: 'output/categories/index.html'
```