Table format

Hey Bryan,

Here is a pass at a different formatter.  I was looking for something that was more pipegreppable.  This probably won't work for everything, but works pretty well for my use-cases so far.  It can be enabled with the settings.  If I pulled together some tests for the formatter, what do you think?

Cheers

```
check                                  client           flapping issued     occurrences status
ping_private_gateway                   endpoint1a6aad84 false    1371722407 23          2
ping_metrics                           endpoint6accbc0d false    1371722404 22          1
ping_private_gateway                   endpoint2a44ba0d false    1371722407 23          2
keepalive                              endpoint3294654a false    1371722459 146         2
keepalive                              endpointe2eae3e3 false    1371722459 147         2
keepalive                              hubot1b          false    1371722459 147         2
```