Support for expanding inside backticks

[certainlyakey]

Continuing with what @wilkystyle has asked: it would be good too have support for expanding to a text inside backticks "`". Probably will be useful for anybody who deals with and reads often Markdown and copies a lot of code strings from there.

[wilkystyle]

Is there any update on this issue, or the direction planned? I see a pretty big pull request (#59) which seems to allow us to define new expansion behaviors (and resolve this issue) pretty easily.

Thanks for this plugin, and for your hard work!

[r-stein]

I am finally going to rework that PR, merge it, and create a pre-release in the next weeks :)