Remove `frameworkVersion` as a mandatory field

:koala: :+1: 

Move the checks for valid frameworkVersions to only apply when app `has_location?`.

When a location is defined, you get the following error still, if you haven't defined your `frameworkVersion`.

![screenshot 2014-02-10 14 13 46](https://f.cloud.github.com/assets/687974/2122033/67d5d5e2-9201-11e3-9424-e5eae8a91dd8.png)

/cc @zendesk/quokka