Preface test files with test

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()