Update version number and update documentation

* Support encryption with OpenSSL (#138)
* Support "include" directive in built-in template processor (#255)
* Support extensions for alternate files and templates (#257)
* Improve support for default branches (#231, #232)
* Add --version and --help as yadm internal commands (#267)
* Improve support for XDG base directory specification
* Use XDG_DATA_HOME used for encrypted data and repository (#208)
* Default repo is now ~/.local/share/yadm/repo.git
* Default encrypted archive is now ~/.local/share/yadm/archive
* Improve shell completions (#238, #274, #275)
* Remove support for YADM_COMPATIBILITY=1 (#242)
* Remove deprecated option cygwin-copy
* Fix template mode inheritance on FreeBSD (#243, #246)
* Fix hook execution under MinGW (#150)
* Improve compatibility with Oil shell (#210)

CONTRIBUTORS

@@ -2,8 +2,10 @@ CONTRIBUTORS
 
 Tim Byrne
 Martin Zuther
+Erik Flodin
 Jan Schulz
 Jonathan Daigle
+Luis López
 Tin Lai
 Espen Henriksen
 Cameron Eagans
@@ -11,6 +13,7 @@ Klas Mellbourn
 Ross Smith II
 Tomas Cernaj
 jonasc
+Chad Wade Day, Jr
 Sébastien Gross
 David Mandelberg
 Daniel Gray
@@ -25,7 +28,10 @@ Daniel Wagenknecht
 Stig Palmquist
 Patrick Hof
 con-f-use
+Travis A. Everett
 Sheng Yang
+Adam Jimerson
+addshore
 Tim Condit
 Thomas Luzat
 Russ Allbery