Add 4x speed improvement by avoiding redundant I/O

Generating the simple summary page was taking 10+ seconds on my laptop.
By remembering which coordinate files have already been read instead of
re-reading them, this version runs in about two and a half seconds,
which will make further improvements to the report much less painful to
experiment with.
Add a grid for each tool setting it vs. all others

This lets the author of any one of the tools in question get, in a
single place, a summary of which of the other tools (if any!) their
results agree with.
Merge pull request #28 from brandon-rhodes/feature/grid

Possible way to display each tool against all others