Update changelog for version 15

changes.rst

 Change Log
 ==========
 
-Version 15 (unreleased)
+Version 15 (2020-01-15)
 -----------------------
 
-.. rubric:: General
-
-.. rubric:: Getting Started Checklist
-
 .. rubric:: Observing Capabilities
 
 *  Add sensitivity, detection rate, and localization accuracy statistics for O3
@@ -16,14 +12,6 @@ Version 15 (unreleased)
    sources. Update O3 timeline and range schedule figures. Expect another
    update in the next few weeks incorporating O3a.
 
-.. rubric:: Data Analysis
-
-.. rubric:: Alert Contents
-
-.. rubric:: Sample Code
-
-.. rubric:: Additional Resources
-
 Version 14 (2020-01-06)
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