Check error handlers for specific classes first

This allows adding error handlers like this:

    @app.errorhandler(werkzeug.exceptions.Forbidden)

And subclassing HTTPExceptions:

    class ForbiddenBecauseReason(Forbidden): pass

    @app.errorhandler(ForbiddenBecauseReason)
    def error1(): return "Forbidden because reason", 403
    @app.errorhandler(403)
    def error2(): return "Forbidden", 403

... the idea being, that a flask extension might want to raise an
exception, with the default behaviour of creating a HTTP error page,
but still allowing the user to add a view/handler specific to that
exception (e.g., "Forbidden because you are not in the right group").
Fix import in viewdecorators.rst for @templated
Tweak wording in viewdecorators.rst
Fixed intention in flask init
Added the new flask run module to start the server.
Merge branch 'master' of github.com:mitsuhiko/flask
Added thread flag to flask run
Fixed a reference in the docs.
Added __main__ module
Fix typos in docstrings and comments in run.py
few mispelling errors
Check links in the documentation with tox
Fix Pocoo documentation links
Link to https version of python docs

To which the http version permanently redirects
Fix Jinja link
Switch pypi links to https

To which the http version redirects permanently
Switch packages.python.org to pythonhosted.org
Use https instead of http for docs.python.org
Use https for devcenter.heroku.com
Use libevent.org