testing.txt: Clean up text.
testing.txt: Fix subsubsection delimiters.
testing.txt: Add instructions about ICE_CONFIG.
testing.txt: Correct style and add Sphinx keyword.
testing.txt: Correct syntax and spelling.
testing.txt: Use inline Sphinx syntax.
testing.txt: Oxfordise the list syntax.
testing.txt: Change order of text, update syntax.
testing.txt: Clarify text meaning.
Merge pull request #471 from bpindelski/rebased/develop/testing-clean

Clean up testing.txt (rebased onto develop)