I think a really cool new markdown editor that I discovered a little over a month ago is Stackedit: https://stackedit.io/
Stored locally or on DB/GDrive, latex support, and a very complete product. The interface is a little unintuitive at first, but I highly suggest anyone that writes blog posts in markdown to check it out.
+1 for stackedit. The biggest point is that it's open source [1] under Apache License.