Fix broken image in README.

Author: benmills

README.mkd

@@ -2,7 +2,7 @@
 
 Easily interact with tmux from vim.
 
-![vimux](https://www.braintreepayments.com/assets-a5fdbbf08b/assets/images/blog/vimux3.png)
+![vimux](https://www.braintreepayments.com/assets/images/blog/vimux3.png)
 
 What inspired me to write vimux was [tslime.vim](https://github.com/kikijump/tslime.vim), a plugin that lets you send input to tmux. While tslime.vim works well, I felt it wasn't optimized for my primary use case which was having a smaller tmux pane that I would use to run tests or play with a REPL.