add code to create the vertex shader
use pattern rule to remove rule duplication
use cc extension instead of cpp
add initial support for Google Test framework

- Copy the sample gtest Makefile as gtest.mk to keep it separate from
  our main Makefile. Someday we move these rules back to the main
  Makefile if we can clean them up.

- Tweak the variables in there to create a test from some stub code.

- Call this extra Makefile from our main Makefile.

- Update the .gitignore to ignore the gtest by products.

- You will need to download Google Test from the website and unzip into
  the root folder of this project and then run "make test". The test
  rule does not yet run the tests automatically.
add a rule to build and execute all tests
use parents in Makefile
move source files to src directory
rename obj directory to out
use order-only prerequisites for out directory