Reference AtChem

[stulacy]

AtChemOnline should be referenced with both the tutorial and a link to the webpage. Also there could be some mention of AtChem2.

[stulacy]

The AtChemOnline tutorial is now available through the top navigation bar, which also provides a link to the webpage. This issue is therefore partially addressed, although there is no mention of AtChem2.
However, there are plans to update AtChemOnline to use AtChem2, which would provide a good excuse to revisit the AtChem material on the MCM site, so I'll leave this issue open.