mathjax iframe injection
Merge branch 'develop' into feature/mathjax

Conflicts:
	js/views/reader_view.js
Merge branch 'develop' into feature/mathjax

Conflicts:
	js/views/reader_view.js
added mathjax call
loading mathjax on demand
Implement iframe content, script, and reading system object injection.
Merge branch 'feature/iframe_injection' into feature/mathjax

Conflicts:
	js/views/reader_view.js
Pass mathjax url to iframe loader.
Inject mathjax script
Disable old mathjax injector function for now.
Don't re-use the same iframe element for reflowable layouts.
Instead destroy and create one every spine item change.
This fixes an issue in where MathJax does not reinitialize on spine item document changes.
Inject reading system object before writing to the iframe DOM.
Remove previous attempt at reading system injection.
Merge branch 'feature/iframe_injection' into feature/mathjax

Conflicts:
	js/views/iframe_loader.js
Disable the remove parent inline script injection.
Disabling absolute URI base href hack (loses compatibility for IE<11)
Merge branch 'develop' into feature/mathjax

Conflicts:
	js/views/reflowable_view.js
Use Blob URLs for iframe content injection.
This is now used in favor of the document.write approach because XHTML needs to be parsed and rendered properly.
Merge branch 'develop' into feature/mathjax
Fix small refactoring problem.
Clean up.