Prepare v0.7.1 bugfix-release

[andrjohns]

Submission Checklist

• [x Run unit tests
• Declare copyright holder and agree to license (see below)

Summary

Bumping DESCRIPTION for release

Copyright and Licensing

Please list the copyright holder for the work you are submitting
(this will be you or your assignee, such as a university or company):
Andrew Johnson

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[jgabry]

Thanks for doing this! I feel behind on everything while traveling abroad for a few weeks.