Added ability to create multiple tests in a dir.

Before, only one source file could be present in a test directory. This
was annoying me so I went in, created a dummy test-2 file in searching
and modified the make rules for tests to now build all .cpp files
and create executables for them. Now the test file names can be more
specific as to what they test.

Modified how the makr vars SRCS and PROGS were created as well, now you
don't have to explicitly type out the names, everything is named off of
how you name your actual .cpp file.

Removed depend from top-level make rules since my impl has been removed
for now.