Use preq in the web handler & bump preq version to 0.2.6
Improve error logging

Always log full error information including request & response in
handleResponse.
Fix cleandb.sh script

Note: Those hash sections include the bucket name, so will change when the
bucket name changes.
Bump preq up to 0.2.7

The constructor-style call was not properly tested in preq, and remote request
failures were covered up locally by the broken cleardb.sh script. Preq 0.2.7
fixes the issue, so bump the dependency.