remove mention of "borg" in changelog title

we know what we are looking at already...

also demote the attic changelog so it doesn't show in the main table
of contents.

docs/changes.rst

@@ -1,5 +1,5 @@
-Borg Changelog
-==============
+Changelog
+=========
 
 Version 0.27.0
 --------------
@@ -345,20 +345,20 @@ Other changes:
 
 
 Attic Changelog
-===============
+---------------
 
 Here you can see the full list of changes between each Attic release until Borg
 forked from Attic:
 
 Version 0.17
-------------
+~~~~~~~~~~~~
 
 (bugfix release, released on X)
 - Fix hashindex ARM memory alignment issue (#309)
 - Improve hashindex error messages (#298)
 
 Version 0.16
-------------
+~~~~~~~~~~~~
 
 (bugfix release, released on May 16, 2015)
 - Fix typo preventing the security confirmation prompt from working (#303)
@@ -368,7 +368,7 @@ Version 0.16
 - Fix parsing of iso 8601 timestamps with zero microseconds (#282)
 
 Version 0.15
-------------
+~~~~~~~~~~~~
 
 (bugfix release, released on Apr 15, 2015)
 - xattr: Be less strict about unknown/unsupported platforms (#239)
@@ -382,7 +382,7 @@ Version 0.15
 - Include missing pyx files in dist files (#168)
 
 Version 0.14
-------------
+~~~~~~~~~~~~
 
 (feature release, released on Dec 17, 2014)
 
@@ -396,7 +396,7 @@ Version 0.14
 - Fix issue with empty xattr values (#106)
 
 Version 0.13
-------------
+~~~~~~~~~~~~
 
 (feature release, released on Jun 29, 2014)
 
@@ -412,7 +412,7 @@ Version 0.13
 - Fix Python 3.2 specific lockf issue (EDEADLK)
 
 Version 0.12
-------------
+~~~~~~~~~~~~
 
 (feature release, released on April 7, 2014)
 
@@ -429,7 +429,7 @@ Version 0.12
 - Switch to SI units (Power of 1000 instead 1024) when printing file sizes
 
 Version 0.11
-------------
+~~~~~~~~~~~~
 
 (feature release, released on March 7, 2014)
 
@@ -444,7 +444,7 @@ Version 0.11
 - Ignore xattr errors during "extract" if not supported by the filesystem. (#46)
 
 Version 0.10
-------------
+~~~~~~~~~~~~
 
 (bugfix release, released on Jan 30, 2014)
 
@@ -454,7 +454,7 @@ Version 0.10
 - Make source code endianness agnostic (#1)
 
 Version 0.9
------------
+~~~~~~~~~~~
 
 (feature release, released on Jan 23, 2014)
 
@@ -467,14 +467,14 @@ Version 0.9
 - Improved libcrypto path detection (#23).
 
 Version 0.8.1
--------------
+~~~~~~~~~~~~~
 
 (bugfix release, released on Oct 4, 2013)
 
 - Fix segmentation fault issue.
 
 Version 0.8
------------
+~~~~~~~~~~~
 
 (feature release, released on Oct 3, 2013)
 
@@ -487,7 +487,7 @@ Version 0.8
 
 
 Version 0.7
------------
+~~~~~~~~~~~
 
 (feature release, released on Aug 5, 2013)
 
@@ -498,7 +498,7 @@ Version 0.7
 
 
 Version 0.6.1
--------------
+~~~~~~~~~~~~~
 
 (bugfix release, released on July 19, 2013)
 
@@ -506,6 +506,6 @@ Version 0.6.1
 
 
 Version 0.6
------------
+~~~~~~~~~~~
 
 First public release on July 9, 2013