Blockquotes: Don't merge sequential quotes into a single blockquote

[codebykat]

This fixes the bug reported in #332, where two sequential quotes with whitespace between them get converted to a single blockquote.

The culprit is a whitespace matcher in the regex; I'm not sure what case it is intended to address. All tests pass without it (and I added a new one to demonstrate this issue and fix).

Blockquotes containing internal lines also seem fine, I added a test just to be sure. n.b. It is leaving some spaces (note the ..\n), which I included in the test; that seems like a separate bug. Not introduced in this PR.

  <blockquote>\n
    ..<p>no.way</p>\n
    ..\n
    ..<p>way</p>\n
 </blockquote>\n

[nicholasserra]

Thanks! I'll check this out ASAP. Definitely odd that the regex line is there and has a comment for its purpose, but doesn't seem to fail any tests without. A bit worrisome, but i'll take a good look at it.