Update description field in Cabal file.

Ignore-this: 2c7c554fe738aa8b1508130f7bf8f319

darcs-hash:20140731224103-4d2ae-73ac5362ee3990c4605d041f7fa3efa30c61ed3a
Increase version to 0.3.1.1 and update changelog.

Ignore-this: 27513ce55397d66084e91d421476c810

darcs-hash:20140731224140-4d2ae-dba4d91c8ed4a7e7c18fa3ba3da8b5adb6898483
Add missing header file for fprintf.

Ignore-this: a48a6217a3e523214c23f400abec5dcc

darcs-hash:20140731224934-4d2ae-277d9e30713aa4f194c718235a49880e9510ed99