Add documentation of versioning/branches to main README (#163)

* update readme to explain versioning

* add detail to versioning docs

* clarify language in README on versioning and bump version

Author: Zsailer

README.md

@@ -21,11 +21,23 @@ You can find the installation documentation for the
 The documentation for advanced usage of Jupyter notebook can be found
 [here](https://jupyter-server.readthedocs.io/en/latest/).
 
-For a local installation, make sure you have
+To install the latest release locally, make sure you have
 [pip installed](https://pip.readthedocs.io/en/stable/installing/) and run:
 
     $ pip install jupyter_server
 
+### Versioning and Branches
+
+If Jupyter Server is a dependency of your project/application, it is important that you pin it to a version that works for your application. Currently, Jupyter Server only has minor and patch versions. Different minor versions likely include API-changes while patch versions do not change API.
+
+When a new minor version in released on PyPI, a branch for that version will be created in this repository, and the version of the master branch will be bumped to the next minor version number. That way, the master branch always reflects the latest un-released version.
+
+To see the changes between releases, checkout the [CHANGELOG](https://github.com/jupyter/jupyter_server/blob/master/CHANGELOG.md).
+
+To install the latest patch of a given version:
+
+    $ pip install jupyter_server>=0.2
+
 ## Usage - Running Jupyter Server
 
 ### Running in a local installation

jupyter_server/_version.py

@@ -9,5 +9,5 @@
 
 # Next beta/alpha/rc release: The version number for beta is X.Y.ZbN **without dots**.
 
-version_info = (0, 2, 0, '.dev0')
+version_info = (0, 3, 0, '.dev')
 __version__ = '.'.join(map(str, version_info[:3])) + ''.join(version_info[3:])