Clarify docs regarding add_attachment()
Clarify docs regarding add_attachment()

m42e/jira,pycontribs/jira,coddingtonbear/jira,VikingDen/jira,stevencarey/jira,rayyen/jira,dbaxa/jira,m42e/jira,pycontribs/jira,systemadev/jira-python,dbaxa/jira,awurster/jira,systemadev/jira-python,stevencarey/jira,rayyen/jira,milo-minderbinder/jira,milo-minderbinder/jira,jameskeane/jira-python,akosiaris/jira,VikingDen/jira,akosiaris/jira,tsarnowski/jira-python,coddingtonbear/jira,kinow/jira,tsarnowski/jira-python,jameskeane/jira-python,dwmarshall/pycontribs-jira,kinow/jira,dwmarshall/pycontribs-jira,awurster/jira