Add option to wait for AWS CF command complete
DRY up repeated polling code
Merge pull request #75 from kyptin/cf-waiting

Add option to wait for AWS CloudFormation commands to complete
Remove extraneous output
Add CloudFormation convenience functions

Instead of calling e.g.

    mcv.cloudformation.create_or_update('create', ...)

Now we can simply call

    mcv.cloudformation.create(...)

And ditto for `update`.
Merge pull request #76 from kyptin/cf-conveniences

CloudFormation Conveniences
When a CF stack is rolled back, stop waiting

If CloudFormation encounters a failure when creating or updating a
stack, it will rollback all the changes so that the create or update is
atomic. (This is very nice!)

This commit changes the functions that wait for a stack to be
created/updated so that they detect the rollback and stop waiting,
printing a message to the user that there was an error.
Add functions to get current stack params

The added functions (1) get the parameters that were used to create a
currently running stack and (2) override those current params with the
given params.

These functions seemed useful enough and general enough to go here.
Fix non-conventional parens
Merge pull request #77 from kyptin/cf-stop-waiting-upon-rollback

When a CF stack is rolled back, stop waiting
Merge pull request #78 from kyptin/cf-get-current-params

Add functions to get current stack params
Auto-discover location of `pip`

When `pip` is installed manually it shows up in _not_ `/usr/bin`, but
rather `/usr/local/bin`. Switch to using auto-discovery to find the
appropriate executable.