html_render_diff should ignore case by default

[Mr0grog]

The html_render_diff diff should not be case-sensitive, or it should have an option for case-sensitivity and the default value should not be sensitive. There are two reasons for this:

• We are generally focused on identifying meaningful changes to the content (as opposed to determining exactly what changed between two versions of a page), and changes in case are not important the vast majority of the time.

• We have seen quite a few situations where something may have previously been all-caps, and then changed to be normal case and use CSS to make it all caps. Because the capitalization changed, we highlight it as a difference, even though there is no visual impact. This can be really confusing! For example, the main heading (“OIL AND GAS”) and the “LEARN MORE ABOUT…” text both changed that way in this diff:

  

  (See this live at https://monitoring.envirodatagov.org/page/ad09dc3a-b056-4bba-8b58-8d24b0f3e442/18931102-67d3-4f89-9734-f8dd3e69e338..a72f6986-ccec-46ed-ab42-31370ed2e279)

I’m thinking we’d change html_render_diff.html_diff_render() to have the following signature:

def html_diff_render(a_text, b_text, a_headers=None, b_headers=None,
                     include='combined', content_type_options='normal',
                     url_rules='jsessionid', case_sensitive=False):