Updated changelog

CHANGELOG.txt

 Changes in Release 1.5
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+  * Added binding to 3DComb (structural alignment)
+  * Added functions to predict contacts from multiple sequence alignments
+  * Added some functions to analyze MD trajectories (pairwise distance matrices,
+    pairwise distance fluctuations, RMSD matrix etc.)
+  * Support of non-orthogonal unit cells for wrapping entities
+  * Flexible implementation of HBPlus
   * Updated dependencies (Eigen2 to Eigen3, Boost 1.47 to 1.53)
   * Wrapper for OpenMM. This allows for direct access to molecular mechanics
     functionality from within OST.