preserve font-style/font-weight

fixes https://anki.lighthouseapp.com/projects/100923-ankidesktop/tickets/333-html-being-changed-after-the-card-is-created

aqt/editor.py

@@ -275,6 +275,8 @@ def _filterHTML(html):
                 continue
             if k.strip() == "color" and not v.strip() == "rgb(0, 0, 0)":
                 preserve += "color:%s;" % v
+            if k.strip() in ("font-weight", "font-style"):
+                preserve += item + ";"
         if preserve:
             # preserve colour attribute, delete implicit class
             tag.attrs = ((u"style", preserve),)