Roll Observatory packages and add a roll script

packages/quiver/CONTRIBUTING.md

+# How to contribute
+
+### Sign our Contributor License Agreement (CLA)
+
+Even for small changes, we ask that you please sign the CLA electronically
+[here](https://developers.google.com/open-source/cla/individual).
+The CLA is necessary because you own the copyright to your changes, even
+after your contribution becomes part of our codebase, so we need your permission
+to use and distribute your code. You can find more details
+[here](https://code.google.com/p/dart/wiki/Contributing). You'll only need to
+do this once.
+
+### Contribution Guidelines
+
+We welcome your pull requests, issue reports and enhacement requests. To make
+the process as smooth as possible, we request the following:
+
+   * Sign the [CLA](https://cla.developers.google.com/about/google-individual)
+     (see above) before sending your pull request. It's quick, we promise!
+   * Have test cases for your changes and ensure that the existing ones pass in
+     checked mode.
+   * Run your changes through `dartformat`. Follow the installation instructions
+     in the [dart_style](https://github.com/dart-lang/dart_style) README for
+     more info.
+   * Squash your commits into a single commit with a good description. You can
+     use `git rebase -i` for this. For more details on rebasing, check out
+     Atlassian's
+     [tutorial](https://www.atlassian.com/git/tutorials/rewriting-history).
+   * During code review, go ahead and pile up commits addressing review
+     comments. Once you get an LGTM (looks good to me) on the review, we'll ask
+     you to squash your commits one last time, then we'll be good to merge!