gwpy/gwpy: 0.12.1

Bug-fix release for gwpy-0.12 Bug-fixes (including package, unit test, and documentation updates): [#891, #899, #903] reverted auto-cropping of output series for TimeSeries.whiten [#900] moved TimeSeries.shift to Series [#904] fixed bug in writing FrDetectors to GWF with lalframe backend [#882, #884, #898] misc bug fixes for gwpy.cli [#906] updated license to GPLv3+ [#898, #908] misc documentation improvements See https://github.com/gwpy/gwpy/compare/v0.12.0..v0.12.1 for full details of what has changed since the last release