Revert relying on git for version

Even on a tag, this is adding the SHA to the version and messing up
runtime parsing of it, which the Riak backend does to determine if an
upgrade is necessary. We will keep manually updating the version number
for now.

src/bitcask.app.src

@@ -1,7 +1,7 @@
 {application, bitcask,
  [
   {description, ""},
-  {vsn, git},
+  {vsn, "1.7.2"},
   {modules, []},
   {registered, []},
   {applications, [