Test backcompat for pre-0.9.1 compiled templates

We run the entire suite of tests as we had on
0.9.0 against an old version of compiled templates.
The test suits is found in old_templates_tests.js

Why? Packages are published in built form. With Meteor 0.9.1, we
didn't bump the major version of the 'templating' package (which
would force packages that define templates to publish new versions
of their package). Instead, we decided to keep backcompat with the
old Blaze runtime APIs.

If these tests ever break in the future, and backcompat is too hard
to achieve (or undesirable), we can simply bump the major version
of the 'templating' package, and get rid of these tests.