Empty lines should not be parsed as paragraphs. This was happening
in determined circumstances.
For instance, when stripping reference style links, `\n\n` was left being,
creating an undesired empty paragraph. This commit fixes the issue.
Closes#334
When using html pre/code tags to wrap github's fenced code block syntax,
showdown would parsed them instead of treating them like plain code.
Closes#229
Enable parsing markdown inside HTML blocks if those blocks have an attribute called markdown="1".
This feature is EXPERIMENTAL! As such, the behavior might change on future releases.
Closes#178