replaces sed with elisp in re-tag action
* mu4e: replaces sed with elisp in re-tag action
mu4e: fixes new elisp re-tag implementation for forward slashes
* mu4e: uses correct helper function naming conventions.
* mu4e: Whoops, uses actual correct helper function naming conventions (~ instead of -)
Merge pull request #158 from pygatea/master

* re-implements "retagging" action in elisp to get around sed version inconsistencies between platforms