Misspelling uppercase insert -> Insert image 3-8

Cause the misspelling the website do not show the figure in the html tag but only print [..]insert 18333fig0308.png [..]
Merge pull request #871 from byteriot/patch-1

Misspelling uppercase insert -> Insert image 3-8
Add a test on badly formated insert directive

The directive for inserting an image is:

 Insert <image>
Merge branch 'progit/master'