Fix syntax error (issues #7, #12, #14)

[ninja-left]

Fix

• Fix SyntaxError: Generator expression must be parenthesized (https://github.com/rdegges/brute/issues/14, https://github.com/rdegges/brute/issues/12, https://github.com/rdegges/brute/issues/7)

Added parenthesis around generator

[ninja-left]

Hello I patched brute.py and fixed issues #7 #12 #14 . I would want maintainers to review and approve/reject my PR. You may view the unified diff file using below link. Patch file

@rdegges , @f-prime , @zhao-ji , @petermuller