FIx AA_MODEL meta-data bug

The mechanism for AA_MODEL was error-prone in that it assumed the
application package name would always match the src code package
name. This made it easier to define AA_MODEL classes by using
shortcut notation. Unfortunately, this is problematic when the
application package name differs from the src code package name,
which comes up most often with Gradle build variants where the
application package name changes on a build by build basis.
Fix bug introduced from previous commit

I was not accounting for how the list of models have leading spaces so it would
fail to find the class.
Better error message for devs on malformed meta-data
Revert "Better error message for devs on malformed meta-data"

This reverts commit 6550761e8e75757b74168e99717e13dace8da302.

Apparently this can't be done because sometimes the table info
and serializer info is meant to fail, I think.
Use TextUtils.isEmpty() instead of String.isEmpty() as the latter is only available in API > 8
Merge pull request #173 from Jonan88/master

Fix compilation on SDK < 9
Merge branch 'master' of https://github.com/pardom/ActiveAndroid
Merge pull request #134 from bradmcmanus/master

FIx AA_MODEL meta-data bug
Merge branch 'master' of https://github.com/pardom/ActiveAndroid