Add a travis-ci.org build status PNG to README
Issue #1: Validate developer properties

* Validate developer as object

* Validate developer.name as string

* Validate developer.url as URL

* Rework schema validation to be recursive
Merge pull request #19 from lmorchard/add-travis-status

Add a travis-ci.org build status PNG to README
Issue #1: Tweaks
Merge pull request #18 from lmorchard/1-developer-props

Issue #1: Validate developer properties
Issue #3: Validate installs_allowed_from
Issue #3: Ensure installs_allowed_from is not empty when present
Issue #3: Use unique keys for each validation condition
Fix issue #4: Validate screen_size
Closes #7: Validate type

* Ensure app type is web, privileged, or certified

* Tweak installs_allowed_from check for listed app

* Add options parameter to validate, for out of band info like whether
  the app's intended to be packaged and/or listed

* Tweak .gitignore to leave out VIM swapfiles
Delete type from the todo list
Close #16: Validate fullscreen