Do not create a hashtag link if tag is all numerics

*[implemented on 7aug2013]*

typically, when a pound sign preceds text that contains all digits, then it's not a real hashtag and more of a number, such as a ranking.

so ignore hashtags if the tags is all digits. user can add one alpha or an underscore if the all-numeric tag is meant to be a hashtag.

#resolved
#junco