Update version bump process

Why is this change needed?
--------------------------
We should rely on the generator to change the version number in all the
various generated locations instead of manually changing it. This will
be less error prone, especially if the locations of the generated
version numbers change.

How does it address the issue?
------------------------------
Switch to updating the version number in the generator config then
regenerating.

Note that `DocRaptor.nuspec` is still manual. Probably the build/release
process should be updated to use `src/DocRaptor/DocRaptor.nuspec`
instead, but that is out of scope for the moment.

Any links to any relevant tickets, articles, or other resources?
---------------------------------------------------------------
https://3.basecamp.com/3093825/buckets/29124557/todos/5284412189
https://3.basecamp.com/3093825/buckets/29124557/todos/5284421778

Any screenshots?
----------------

Did you complete all of the following?
--------------------------------------
- Run test suite?
- Add new tests?
- Consider security implications and practices?

README.md

@@ -64,20 +64,22 @@ The generated client needed a few fixes
 1. Pull latest master
 2. Merge feature branch(es) into master
 3. `script/test`
-4. Increment version in code:
+4. Increment version:
   - `generator-config.json`
-  - `setup.py`
+5. Run `script/generate_language` to update generated version numbers:
+  - `docraptor/__init__.py`
   - `docraptor/api_client.py`
   - `docraptor/configuration.py`
-5. Update [CHANGELOG.md](CHANGELOG.md)
-6. Commit "Release version vX.Y.Z"
-7. Push to GitHub
-8. Tag version: `git tag 'vX.Y.Z' && git push --tags`
-9. Clean out any old packages `rm dist/*`
-10. Build packages `python setup.py sdist bdist_wheel`
-11. Upload packages `twine upload dist/*`
-12. Verify package release at https://pypi.python.org/pypi/docraptor
-13. Update documentation on docraptor.com
+  - `setup.py`
+6. Update [CHANGELOG.md](CHANGELOG.md)
+7. Commit "Release version vX.Y.Z"
+8. Push to GitHub
+9. Tag version: `git tag 'vX.Y.Z' && git push --tags`
+10. Clean out any old packages `rm dist/*`
+11. Build packages `python setup.py sdist bdist_wheel`
+12. Upload packages `twine upload dist/*`
+13. Verify package release at https://pypi.python.org/pypi/docraptor
+14. Update documentation on docraptor.com
 
 
 ## Version Policy