Merge pull request #315 from jasongrout/release

Update release instructions

Author: jasongrout

RELEASE.md

@@ -1,11 +1,10 @@
-
-To create a release, run the following:
+To create a release, update the version number in jupyter_server/_version.py, then run the following:
 
 ```
-git clean -dfx
+git clean -dfxx
 python setup.py sdist
 python setup.py bdist_wheel
-script_version=`python setup.py --version 2>/dev/null`
+export script_version=`python setup.py --version 2>/dev/null`
 git commit -a -m "Release $script_version"
 git tag $script_version
 git push --all