Rename core tests with test_ prefix so django recognizes them

Django 1.6 uses a new test runner which requires tests to be in files
that start with "test". Django 1.5 and earlier would find these in the
tests/ directory but that is no longer the case so we add the test_
prefix which has no negative effects in Django <= 1.5 but allows the
test runner to find them in Django >= 1.6.

Signed-off-by: Don Naegely <naegelyd@email.chop.edu>
Update join creation to support changes made in Django 1.6

Signed-off-by: Don Naegely <naegelyd@email.chop.edu>
Use SelectInfo class in Django 1.6+

This is a new data structure that includes the column and the field
instance.

Signed-off-by: Byron Ruth <b@devel.io>
Add conditional prefix to test modules based on Django version

Django >= 1.6 requires the full test module while Django <= 1.5 could
get by with just the name. The test_suite.py now adds the prefix when it
detects a django version that requires it.

Add Django 1.6.6 to TravisCI build matrix

Signed-off-by: Don Naegely <naegelyd@email.chop.edu>
Update tests to account for extra whitespace in SQL in Django 1.6

Also updates the formatting of the long SQL statements to make them
easier to read.

Signed-off-by: Don Naegely <naegelyd@email.chop.edu>
Fix LazyModelTrees test to prevent testing external state

Signed-off-by: Byron Ruth <b@devel.io>