Previous implementation was always adding a trailing slash to restore
URLs even when the URL point to a file. To make it lean, change the
implementation to avoid trailing slash. Basically, rename the index()
method to default() method.

To support other restore kind, change the url format.

To fix testcases, we need to sort the attributes.

Change attrib() to support True value. Used for selected attribute.
Also fix html escaping.

Don't use it yet. Consider using it only when creating new template or
refactoring.

Make the integration test (java/web tests) working in python2.

Make testcases run in py2 and py3

Ran `futurize --write --nobackups --stage1 --unicode-literals`

translation too.

plugins: LDAP and SQLite. MySQL is on the way.

accepted language.

#23