Add a test for =pod Html

[coke]

Issue #23

[coke]

Here's a very simplistic test, just making sure that no <p>'s were added to the code. (I expected that nothing would change, but this is a start)

[coke]

Branch now has a test and a change to not update html/xhtml sections at all. All tests (including the new one) pass

[coke]

I'm still not convinced this is 100% right, though.

[tisonkun]

If all text inside =pod Html is raw HTML, it's right. Because Pod machinery wrap para into Pod::Block::Para.

However, users might using pod6 code inside Html block, which cause type object insert inside Html, like C<code> generate Pod::FormattingCode<140289445450176> . Thus I use node2rawtext instead, and now C<code> -> code. Anyway, do not using pod6 at all is recommended.

Remain the unescape in order to meet case when someone wants to write C<> or B<> literally for some reason. Although it results < should be written as <, both of them are rare usage, possibility ahead convenience.