make interactive2 tests run as part of make test

Summary:
We previously had interactive2 test inside the interactive2 folder.
This commit adds those to the test infrastructure already in the
top-level perseus Makefile. yay tests!

Test Plan:
    make test
    make jest

Note: make jest is currently [still] failing due to
https://github.com/facebook/jest/issues/62

Reviewers: charlie

Reviewed By: charlie

Subscribers: jlfwong

Differential Revision: http://phabricator.khanacademy.org/D11186