In #18

When Markdown Editor opens (or GFM View is activated),
if .md.html already exists, show it in the View, whatever current mode is (Linked or not)

I have README.md and .README.md.html,
README is from library (that is not edited),
I just want to see it, so I select Show in GFM VIew

Then I just see error Dialog (due to network problem or because I am offline)