Update ahat version number to 1.6

Test: m ahat-test
Test: open heap dump and verify version number on overview page.
Change-Id: I81b91ae954249477b082b3e599fed99873dbbadd
diff --git a/tools/ahat/README.txt b/tools/ahat/README.txt
index e2796aa..12d3aa8 100644
--- a/tools/ahat/README.txt
+++ b/tools/ahat/README.txt
@@ -52,7 +52,17 @@
  * Request to be able to sort tables by size.
 
 Release History:
- 1.6 Pending
+ 1.7 Pending
+
+ 1.6 July 24, 2018
+   Distinguish between soft/weak/phantom/etc references.
+   Annotate $classOverhead byte[] arrays with their class.
+   Show progress of heap dump processing.
+   Add --retained command line option to ahat.
+   Support heap dumps generated with HotSpotDiagnosticMXBean.
+   Updated public APIs for dominators computation, reachability and parser.
+   AhatInstance no longer implements DominatorsComputation.Node
+   Bug fixes.
 
  1.5 December 05, 2017
    Distinguish between weakly reachable and unreachable instances.
diff --git a/tools/ahat/etc/ahat.mf b/tools/ahat/etc/ahat.mf
index df96483..8ce9863 100644
--- a/tools/ahat/etc/ahat.mf
+++ b/tools/ahat/etc/ahat.mf
@@ -1,4 +1,4 @@
 Name: ahat/
 Implementation-Title: ahat
-Implementation-Version: 1.5
+Implementation-Version: 1.6
 Main-Class: com.android.ahat.Main