allow mako.reload_templates override
remove python 2.5, why was it there??
allow relative-template lookup if not found in search paths
update docs and changelog
unused import
Merge branch 'feature.renderer-relative-paths'

This updates the renderer relative paths to be much cleaner, if it is
not found in the usual search directories, then it will fall back to
relative path.

Thanks to @mmerickel for working on this and getting this support in,
this will allow pyramid_mako to be used without setting
mako.directories, thus falling in line with the other renderers that are
available.

Closes #16
Add test case for not isrelspec and failed lookup
Remove unnecessary DummyRenderer