Merge pull request #68 from paulvojta/master

Fixed bug 2941 (or worked around it).  Also cleaned up the output somewhat.
Relax error tolerance slightly.
Replace broken popup htmlLink to file units.html with helpLink("units").
Delete javascript header that created broken link.
Replace broken htmlLink to units.html with helpLink("units").
Fix typos.
Merge pull request #69 from gajennings/units

Thanks!
Added solution from another (duplicate) problem
Added solution from another (duplicate) problem
Added solution
Fixed TeX errors in solution and removed questionable notation