Fix #1198, enable custom locale in template rendering, fixes links

reverts getpelican/pelican@ddcccfeaa952d2e1e24ceac94e5d66c73b57c01b

If one used a locale that made use of unicode characters (like et_EE.UTF-8)
the files on disk would be in correct locale while links would be to C.

Uses a SafeDatetime class that works with unicode format strigns
to prevent ascii decoding errors with Python2.