Updated text justification from 10 characters to 20

Performance flavors were added to the rackspace flavors list and
they have a bit more text than the standard flavors. This caused a confusing
looking list like:

7         15GB Standard Instance
8         30GB Standard Instance
performance1-11 GB Performance
performance1-22 GB Performance

Updated it to look like:

7                   15GB Standard Instance
8                   30GB Standard Instance
performance1-1      1 GB Performance
performance1-2      2 GB Performance
Merge pull request #29 from riltsken/update_flavor_text_justification_for_performance_flavors

Updated text justification from 10 characters to 20