docs: Move README.dev.md into ReadTheDocs.

Fixes: #669.

README.md

@@ -104,7 +104,7 @@ PostgreSQL extension][tsearch], as separate repos.
 contributing!
 
 [cla]: https://opensource.dropbox.com/cla/
-[dev-install]: https://github.com/zulip/zulip/blob/master/README.dev.md
+[dev-install]: https://zulip.readthedocs.io/en/latest/dev-overview.html
 [doc]: https://zulip.readthedocs.io/
 [doc-commit-style]: http://zulip.readthedocs.io/en/latest/code-style.html#commit-messages
 [doc-dirstruct]: http://zulip.readthedocs.io/en/latest/directory-structure.html

docs/dev-overview.md

@@ -1,5 +1,4 @@
-
-Installing the Zulip Development environment
+# Development environment overview
 
 * [Development environment setup for first-time
   contributors](#development-environment-setup-for-first-time-contributors)
@@ -49,8 +48,7 @@ See [the Docker instructions](https://zulip.readthedocs.io/en/latest/install-doc
 
 [using-dev]: https://zulip.readthedocs.io/en/latest/using-dev-environment.html
 
-Using the Development Environment
-=================================
+## Using the Development Environment
 
 See [this guide](https://zulip.readthedocs.io/en/latest/using-dev-environment.html).
 

docs/index.rst

@@ -62,6 +62,7 @@ Contents:
    :maxdepth: 2
    :caption: Installation for developers
 
+   dev-overview
    dev-env-first-time-contributors
    brief-install-vagrant-dev
    install-ubuntu-without-vagrant-dev