Corrected 1 more space issue, added <hr> to common-attributes-include.markdown

Internal links do not work when they are spliced on the markdown page:
[Common Attributes Section][Promise Types and 
Attributes#Common Attributes] 

The entire link must be on the same line:
[Common Attributes Section][Promise Types and Attributes#Common Attributes]

I also added a horizontal line <hr> to the macro in order to visually separate the common attributes from the other attributes on each Promise Type page. (I will remove it if it looks bad.)