Fix image tags by adding a "/" at the end, because some blogs won't create html code correctly

The new fix_tags function can be extended to add different fix when we'll need it.
Try to replace image by its alt value if this one is given
v1.0.1
Merge branch 'epub-plugin' of adorsaz.ch:leed-market into epub-plugin
v1.0.2 (sorry, didn't remember that  1.0.1 already existed !)