Merge pull request #900 from gwaldo/0.9.x

Describe use of 'group' to have multiple values in areaBetween to 0.9.x branch
backport initial version of 0.9.13 release notes, refs #893
Merge pull request #902 from obfuscurity/backport_0_9_13_release_notes

Backport initial version of 0.9.13 release notes to 0.9.x
missing backticks
Merge pull request #903 from obfuscurity/missing_backticks

missing backticks
mention #89
Merge pull request #906 from obfuscurity/backport_mention_pr89

Backport mention #89 in release notes to 0.9.x
typo
Merge pull request #908 from obfuscurity/backport_pickle_typo

Backport typo for release notes to 0.9.x