added some tests for old style string formatting for signed integer decimals
added some tests for old style string formatting for signed integer decimals

JohnDenker/brython,rubyinhell/brython,firmlyjin/brython,brython-dev/brython,olemis/brython,brython-dev/brython,Mozhuowen/brython,kevinmel2000/brython,Hasimir/brython,nvoron23/brython,JohnDenker/brython,firmlyjin/brython,olemis/brython,jonathanverner/brython,firmlyjin/brython,amrdraz/brython,kevinmel2000/brython,molebot/brython,nvoron23/brython,rubyinhell/brython,kikocorreoso/brython,molebot/brython,molebot/brython,Hasimir/brython,Isendir/brython,olemis/brython,Hasimir/brython,firmlyjin/brython,rubyinhell/brython,firmlyjin/brython,nvoron23/brython,brython-dev/brython,rubyinhell/brython,molebot/brython,JohnDenker/brython,amrdraz/brython,kikocorreoso/brython,jonathanverner/brython,Lh4cKg/brython,jonathanverner/brython,kevinmel2000/brython,Isendir/brython,olemis/brython,Mozhuowen/brython,Lh4cKg/brython,amrdraz/brython,JohnDenker/brython,kikocorreoso/brython,Lh4cKg/brython,amrdraz/brython,Mozhuowen/brython,kevinmel2000/brython,Hasimir/brython,Mozhuowen/brython,Isendir/brython,Isendir/brython,Lh4cKg/brython,jonathanverner/brython