Add test script that does the actual testing

Add test script that does the actual testing

Implement test script in bash that handles the testing logic.
Also change Makefile and src/main.c a little to accomodate the changes.
The test script handles the following functionality:
- Handle creation of correct results to compare with
- Recompile gnl functions for testing with different BUFFER_SIZE
- Run the tester executable on tests in test_files/
- Print the results of the test in color including the output of
	valgrind and diff when necessary.