Merge branch 'release' into 'master'

Release v1.0.0-beta.6.

See merge request pubsweet/pubsweet-cli!115

package.json

 {
   "name": "pubsweet",
-  "version": "1.0.0-beta.5",
+  "version": "1.0.0-beta.6",
   "description": "Pubsweet command-line interface, app generator and manager",
   "bin": "./bin/pubsweet.js",
   "scripts": {