This fixes some wording that implies C++98 standard, updates
the recommended solution to looped SECTION macros and mentioned
the "last section failed, test needs to be rerun" problem.
Related to #1367
Related to #1384
Related to #1389
It contains known limitation such as the fact that Catch is not thread
safe, it does not support running tests in forked process or running
multiple tests in parallel
closes#399closes#681closes#246closes#483