pretty print for topic_compare.py

pretty print like following:
```
$ rosrun jsk_topic_tools topic_compare.py /origin /origin /half                  
subscribed as 0: /origin
subscribed as 1: /origin
subscribed as 2: /half

           Name   avg/sec   avg/msg   min/msg   max/msg     quant
        /origin    0.09KB    0.00KB    0.00KB    0.00KB        10
        /origin    0.09KB    0.00KB    0.00KB    0.00KB        10
          /half    0.04KB    0.00KB    0.00KB    0.00KB         5

           Name   avg/sec   avg/msg   min/msg   max/msg     quant
        /origin    0.08KB    0.00KB    0.00KB    0.00KB        20
        /origin    0.08KB    0.00KB    0.00KB    0.00KB        20
          /half    0.04KB    0.00KB    0.00KB    0.00KB        10

```