rewrite to markdown

ChangeLog.rst

-Changelog for tahoe-ssk
-=======================
+# Changelog for tahoe-ssk
 
-0.2.1.0
--------
+## 0.2.1.0
 
 * Add Ord instances for StorageIndex, Verifier, Reader, and Writer.
 * Add ConfidentialShowable instances for SDMF, Verifier, Reader, and Writer.
 * Deprecate dangerRealShow.
 
-0.2.0.0
--------
+## 0.2.0.0
 
 * Add the IV as a parameter to Tahoe.SDMF.encode.
   The IV must be the value used to create the ciphertext so Tahoe.SDMF.encode cannot randomly generate one.
 * Add Tahoe.SDMF.randomIV for randomly generating a new IV.
 
-0.1.0.0
--------
+## 0.1.0.0
 
 * Initial release.
 * Very basic non-verifying decoding support.