Fix error handling and add custom error pages for 404 and 500.
Move templates/, static/, assets.py out of frontend module.
Move create_app() out of frontend module and fix imports.
Merge branch 'develop' of github.com:peterhil/skeleton into develop
Fixes error handling.

Conflicts:
	app/frontend/__init__.py
Merge branch 'develop' into semantic-ui

Conflicts:
	app/static/font/glyphicons-halflings-regular.eot
	app/static/font/glyphicons-halflings-regular.svg
	app/static/font/glyphicons-halflings-regular.ttf
	app/static/font/glyphicons-halflings-regular.woff
	app/static/less/bootstrap/bootstrap.less
	app/static/less/bootstrap/theme.less
	app/static/less/bootstrap/variables.less