Improve "Creating posts" & "Publishing" in readme

This commit adds a little more information to help people contribute to
the blog.

Change-Id: Ic8b6f42949a5c78027d26ac551b03a6411640e6d
Reviewed-on: https://gerrit.causes.com/22991
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>
Tested-by: Joe Lencioni <joe.lencioni@causes.com>