test.project() tests all files in tests directory

Currently running test.project does nothing on a default project, which makes it appear to be broken

Original implementation used testthat's test_directory() function
This required that all test files be prefixed with test-

Adding this prefix is distracting since all code is in a tests directory already

Instead grab all files in tests directory and send to test_file()

Set enclosure environment for test_file

test_file() assumes that we are testing from the global environment
Since we are testing within a function, we need to pass the function's environment as the enclosure

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()

Explicitly get package test variables from globalenv()

testthat runs it's tests in a new environment
ProjectTemplate runs the data readers in the global environment
For package tests to work, variables must be fetched explicitly from the global environment