Preface test files with test

resolves #9

test.project uses test_dir internally, which expects tests to be prefaced by test

Currently running test.project does nothing on a default project, which makes it appear to be broken

Modified stub.tests() to prepend test to autogenerated test file

removed test.project from minimal test since there are no tests available in a minimal project
Also test_dir was throwing an error with testthat_0.8 since the tests director was not available
for setwd()

Hi John,

Thanks for releasing ProjectTemplate. This seems to be a really useful tool. I'm taking it for a test spin on a project I'm starting and will send pull requests as I add or update functionality. Hopefully you don't get too tired of me.

I see that you are looking for a project maintainer. I may be interested. Keep me in mind!

Kenton