Python 3 Updates

Ran python-modernizer, this fixed most of the Python 3
incompatibilities.

Had to manually rework the iteration in svg_regex and svg_transform;
.next doesn't exist in Python 3. Wrapped the builtin next function in a
partial for equivalent functionality.

setup.py

@@ -41,7 +41,7 @@ setup (
    author_email = 'codedread@gmail.com',
    url = 'https://github.com/oberstet/scour',
    platforms = ('Any'),
-   install_requires = [],
+   install_requires = ['six>=1.9.0'],
    packages = find_packages(),
    zip_safe = True,
    entry_points = {