Sort argument is accepted (asc and desc only).

@norm
@robyoung
Add integration test for sort query
Remove empty test file
Rename test

@robyoung
@gtrogers
Allow optional trailing slash

@gtrogers
@pbadenski
Update read api tests to use trailing /
Add sort on basic query

@robyoung
@gtrogers
Merge branch 'master' into sort_and_limit

Conflicts:
	backdrop/read/validation.py
Pep8 compliance
Revert "Allow optional trailing slash"

This reverts commit 234e54211f3d6efd25f27be5afb900d790053a16.
Add sorting to group query

@gtrogers
@robyoung
Remove trailing slash from test

It is no longer required

@gtrogers
@robyoung
Refactor datetime helpers in test_support

@gtrogers
@robyoung
Re-add default sort order

@gtrogers
@robyoung
pep8
Add test for alphanumeric sorting on find
Test periodic grouping returns most recent first
Ignore scenarios tagged with wip

If a scenario is tagged with @wip then it will not be run in CI. This is
useful when writing the feature tests before the code.
Add stop flag to behave

Behave doesn't stop and returns a zero exit status on failures. This is
not ideal. Passing the stop flag forces it to stop and exit with a
status of one.
Change default sort order to ascending

After discussing with @abersager ascending chronological order is a more
convenient default.