Added STL set to the possible test classes
Use to std::chrono instead of clock
Need c++11 for std::chrono
Usage examples
Don't need to include ctime anymore
Added some usage information
Added STL sets to the comparisons
Merge commit 'c7117e18c7734c27402b97ae11c7d05020ea64c3' into soda-submission

This has updated experiments that include a comparison with the C++
STL set class.
Mainly responses to SODA feedback.

One SODA referee seemed to think that we don't understand why hashing
is not a replacement for binary search trees, based on the fact that we
call our data structure a comparison-based dictionary.  We now point
out that at least four other papers call these things comparison-based
dictionaries.

Another referee said he would like to see a comparison with a more standard
implementation like the STL set class.  I already did on July 28th, so
I merged that commit here. The STL set class performs indistinguishably
from my implementation of red-black trees.