Build production versions of the extensions on Travis

Add MathJax config option allign left.

Previously, MathJax was rendering display style math allign: "center",
while KaTeX rendered allign: "left". This has been addressed.

Fix tag search.

This escapes any special url characters in the term

ES stores the tag field as tags

Fix #1879

This contains some potentially confusing code and was clarified by
Randall here: http://git.io/HvLCLA

Set the standalone conversation as the viewer root

This special cases the threads that are styled as cards rather than
replies and allows them to be styled accordingly.

Now the thread is not using negative margins this isn't required.

Fix #1803

Replace documentHelpers with baseURI + URL API

Rather than have a service, ``documentHelpers``, that exposes a value,
``baseURI``, and a function, ``absoluteURI``, decorate ``$document``
so that it's guaranteed to have a ``baseURI`` property and use the
previously included ``URL`` constructor as a standard way to get parts
of a URL.

For readability, especially in light of the injection annotations,
split the app configuration functions in ``app.coffee``.

Clean up unused and duplicate TextHighlight code.

Remove URL fragments

Starve the monkey

As suggested in:

    https://github.com/hypothesis/h/pull/1868/files#r23171034

Annotator#isAnnotator provides better answers as of
openannotation/annotator@368b5cf.

Remove past_data

The processed streamfilter does not send back anything,
more_hits message can give back annotations

This commit is intended as a pure refactoring. No behaviour should be
changed.

There is no need for a variable name if it is just returned immediately.

Allow simple usernames

Simplify the front-end code that transforms annotation permissions
objects into ACLs. Since the front-end does not have to be exposed
to the system principals and special "all" grant used by Pyramid it
only needs to have special handling of the "group:__world__"
principal; others are unused.

Allow the persona filter to pass invalid account URIs through unharmed.