Use (error,result) callbacks for all async methods
Merge pull request #18 from stuartpb/err-res-cbs

Unify function signatures
0.5.0
Partially fixes a bug introduced in #18
Merge pull request #22 from eric-wieser/patch-1

Partially fixes a bug introduced in #18
Prevents callbacks being called multiple times

#18 causes the callback handler to be called multiple times if an error occured.
Merge pull request #23 from eric-wieser/patch-1

Prevents callbacks being called multiple times
Names the middleware function

Provides better debug tracebacks
Merge pull request #24 from eric-wieser/patch-1

Names the middleware function
Adds err parameter to examples

This change brought to you by #18
Merge pull request #25 from eric-wieser/patch-1

Adds err parameter to examples