Ensure ecb's packaging is "MELPA Clean"

[ware]

We need to ensure that ecb is compliant with all aspects of MELPA's expectations for packaging. These include:

• [] The package is released under a GPL-Compatible Free Software License
• [] I've read CONTRIBUTING.org
• [] I've used the latest version of package-lint to check for packaging issues, and addressed its feedback
• [] My elisp byte-compiles cleanly
• [] I've used M-x checkdoc to check the package's documentation strings
• [] I've built and installed the package using the instructions in [CONTRIBUTING.org]

First two are either done or straight forward. The last four I believe all have problems we need to work on.