Add changelog and bump version

Author: LefterisJP

changelog.MD

@@ -0,0 +1,19 @@
+# Emacs Solidity Mode Changelog
+
+The changelog starts from version 0.1.4 as too much was added in each version before that.
+
+## Version 0.1.6
+
+- Add gas estimation code. User facing function is `solidity-estimate-gas-at-point`.
+
+## Version 0.1.5
+
+- Add ability to chain flycheck checkers for solidity.
+- Add `solidity-flycheck-chaining-error-level` so that user can customize
+  the level at which chaining will happen.
+
+## Version 0.1.4
+
+- Integrate with the solium linter
+- Allow specification of solium config file via `flycheck-solidity-solium-soliumrcfile`
+

solidity-mode.el

@@ -4,7 +4,7 @@
 
 ;; Author: Lefteris Karapetsas  <lefteris@refu.co>
 ;; Keywords: languages
-;; Version: 0.1.5
+;; Version: 0.1.6
 
 ;; This program is free software; you can redistribute it and/or modify
 ;; it under the terms of the GNU General Public License as published by