Markdown autolinks <url>
Let the short version of links not have title

and create versions with title with "

Rationale: it is more common to have links without title in Markdown.
Fix markdown fenced code blocks.

Broken because backticks were interpreted as vim code execution.

Also simplified the trigger which was too long and unintuitive.
Merge pull request #483 from cirosantilli/markdown-autolink

Markdown autolinks <url>
Merge pull request #486 from cirosantilli/markdown-link-no-title

Let the short version of links not have title
Merge pull request #487 from cirosantilli/markdown-fix-fenced

Fix markdown fenced code blocks.
Markdown bold and italic