Make sure gitflow config file or branch is not mentioned anywhere.

Abstract out the names.

Change-Id: b35364c3cd
Story-Id: 78913658
Refactoring.

 * Added `panic` function that yells and exits.
 * Minor improvements (less polluted console output etc).

Change-Id: eef659d552
Story-Id: 78913658
Ignore unestimated stories. 

 * I’ve added a `—ignore-unestimated` flag to `pivotal_tools` so that unestimated features are not listed.

Change-Id: 1592804b3c
Story-Id: 78913658
Better handling of existing story branches.

If there’s just one story branch, checkout it.

Change-Id: 142ded5922
Story-Id: 78913658
Install new pivotal shell module too.

Change-Id: ad32122602
Story-Id: 78913658