Print template names rather than objects

[davewsmith]

Resolve issue #127

Show template.name rather than repr(template), and don't mangle the result. For the example in the issue, this produces

AssertionError: Template ndex.html not used. Templates used: ['index.html']

Jinja2 templates don't have names if they're created from strings, but this is a case where assertTemplateUsed() isn't appropriate.