using context:'template' for Nokogiri::HTML5.fragment allows parsing of otherwise illegal fragments like <td>

[jrochkind]

What are you trying to accomplish?

Fixes #2422, and allows render_inline in test to make Nokogiri HTML5 fragments that would otherwise be illegal based on lack of parent context, such as a straight <td> or <tr>

What approach did you choose and why?

Created ticket at nokogiri, sparklemotion/nokogiri#3536, and while the response was that nokogiri was working as expected, as HTML5 rules don't allow context-free parsing generally, and can't parse a (eg) <td> or <tr> without a parent <table>.

However, responder @stevecheckoway, graciously helped us think through it and realize that the (hard to find documented!) context: argument, when passed "template", would trigger HTML5 parsing rules that would allow closer to the arbitrary fragments we are used to with HTML4.

Steve suggested that in retrospect perhaps context: 'template' should have been the default for fragments, instead of "body" which is in fact the default. It's unclear why the context arg hasn't made it into generated nokogiri docs at all!

It's clear to me that this is the right move, and I can't think of any problems or even backwards incompatibilites it would cause.

Anything you want to highlight for special attention from reviewers?

Confirmed new test failed without change.

[jrochkind]

I don't understand the test failures, I don't think they have to do with me?