[#5][xs]: a bit more trimming.
[#5][l]: massive strip down and refactor - getting close.

And we're getting tests!
[#5][s]: refactor to a view in readTextActivity.
[#5][s]: remove forward and back arrow navigation (for the present).
[#5,refactor][l]: simpler non-require setup now working.

e.g. can do (see index.html):

    var text = new Textus.Model.Text({...});
    var viewer = new Textus.Viewer

Essence was:

* merged readTextActivity.js and views/textView.js into js/viewer.js (and reworked to it worked)
* moved views/annotationTypes.js to annotation.js (with appropriate refactoring).
* merged in templates