Fix deprecation with Catalina

Thanks @tattali for your help with this.

I had some complaints that the plugin wasn't working anymore so I updated the XCode project and rebuilt it.

Apparently I was on drugs the last time I released. This is an attempt to remedy some issues created from that. Hopefully this fixes #39 as well.

Adds the code fixes that have been created up to this point. Specifically hopefully fixes the following:

• Doesn't work on Mavericks #29
• Doesn't regonize .md files #25

I'm hoping this will fix issues for Mavericks users. Remember to follow the installation instructions in the Readme.markdown.

Fixes #29