Update changelog for 2.6.

debian/changelog

 tails (2.6) UNRELEASED; urgency=medium
 
-  * Dummy entry.
-
- -- Tails developers <tails@boum..org>  Sat, 10 Sep 2016 11:08:25 +0000
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-tails (2.6~rc1) unstable; urgency=medium
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   * Major new features and changes
-    - Install Tor 0.2.8.6. (Closes: #11351)
+    - Install Tor 0.2.8.7. (Closes: #11351)
     - Enable kASLR in the Linux kernel. (Closes: #11281)
     - Upgrade Icedove to 1:45.2.0-1~deb8u1+tails1: (Closes: #11714)
       · Drop auto-fetched configurations using Oauth2.  They do not