Remove existing documentation.

doc/*.txt
	-Remove existing documentation files.
Add content to README; rename test().

README.md
	-Add a completed "use" section.
	-Add a "scripting" section to document MDL, with most of the
	necessary layout.

src/engine.c
	-Rename `test()` to `sampleAnimation()`.
Finish MDL command documentation.

README.md
	-Finish all command documentation in the "scripting" section.

scripts/test.mdl
	-Remove `test.mdl` because it was only necessary for debugging
	when first implementing MDL animations.
Complete the new README, finish scripting doc.

README.md
	-Complete `MDL` documentation, adding a section about
	transformation and variable mechanics, and another example script.
Add prototype notation doc; example script file.

README.md
	-Add an explanation of command prototype notation.
	-Add information about `make run` and evaluating scripts.

scripts/*.mdl
	-Remove existing `MDL` scripts because they were primarily used
	for testing, and replace them with a single example script.
Merge branch 'feature/doc' into develop

Add scripting documentation and general information to `README.md`.