Add --tag=pre arg to release:pre script

Author: imaustink

package.json

@@ -10,7 +10,7 @@
     "testee": "testee test/browser.html --browsers firefox",
     "preversion": "npm test",
     "postversion": "git push --tags && git push",
-    "release:pre": "npm version prerelease && npm publish",
+    "release:pre": "npm version prerelease && npm publish --tag=pre",
     "release:patch": "npm version patch && npm publish",
     "release:minor": "npm version minor && npm publish",
     "release:major": "npm version major && npm publish"