allow loading of app by path or url from desired capabilities
also a lot of stability improvements and error handling
test url unzipping and make sure we don't cache app accidentally
don't run tests by starting server with app anymore, let's do it all from desired caps
update tests to use desired caps app rather than relying on server
create better test organization, say which tests need --app and which don't
fix unit test
fix various tests based on new structure
Merge pull request #50 from jlipps/master

No longer require --app to start appium; support desiredCaps method