Added tests for ColumnDefault being either callable or scalar
Added tests for ColumnDefault being either callable or scalar

skytreader/wtforms,crast/wtforms,jmagnusson/wtforms,Xender/wtforms,wtforms/wtforms,Aaron1992/wtforms,cklein/wtforms,subyraman/wtforms,hsum/wtforms,Aaron1992/wtforms,pawl/wtforms,pawl/wtforms