fixes a bug with an undefined varaible in the HttpHelper that was
introduced in a recent pull request
Merge pull request #73 from tjmcs/tb/fix-undef-local-var-bug

Fixes #76
Adds code to handle bad HTTP requests in image slice
Merge pull request #82 from tjmcs/tb/fix-image-missing-args-error

Fixes #81 (Internal error thrown by image slice) and fixes #84