Fixes to history page templates

As of now, the (excellent) job history page will only work if luigi is run out of a cloned repo. That is, if I install luigi in a virtualenv called `vendor` and run the scheduler as `vendor/bin/luigid`, the history pages won't render because they can't find the requisite templates. This is because setup.py doesn't add them as package data, and `server.py` isn't looking for them there anyway. I made the following changes which fixed that behavior for me:

* Get templates from dir relative to install (with pkg_resources, like the static files)
* Include templates in package data from setup.py (again like the static files)