fix(HTTPError): Remove dependency on blank title to determine serialization

This patch attempts to make the code easier to understand and maintain
going forward by removing the dependency between the title attribute and
the "serializable" property. The "serializable" property was renamed to
be more indicitive of the context in which it is actually used.

Closes #265
Merge pull request #340 from kgriffs/issues/332

fix(HTTPError): Remove dependency on blank title to determine serialization