added optional length requirement (if entered, length has to be >2 <51)
added optional length requirement (if entered, length has to be >2 <51)

SeanChen0617/flaskbb,lucius-feng/flaskbb,zky001/flaskbb,SeanChen0617/flaskbb-1,emile2016/flaskbb,dromanow/flaskbb,emile2016/flaskbb,SeanChen0617/flaskbb,SeanChen0617/flaskbb-1,realityone/flaskbb,Aaron1992/flaskbb,China-jp/flaskbb,zky001/flaskbb,SeanChen0617/flaskbb,China-jp/flaskbb,Aaron1992/flaskbb,realityone/flaskbb,dromanow/flaskbb,emile2016/flaskbb,lucius-feng/flaskbb,qitianchan/flaskbb,qitianchan/flaskbb,lucius-feng/flaskbb,qitianchan/flaskbb,Aaron1992/flaskbb,dromanow/flaskbb,realityone/flaskbb,SeanChen0617/flaskbb-1,zky001/flaskbb,China-jp/flaskbb