fix (Executor): Improves stacktrace-js integration

This fixes the stacktrace.js integration in two important ways. First, the
library is now beign included externally (much like Fiber). Second, the stack
normalization guards against invalid or unparsable traces (noticed in IE8
compatibility mode).

As part of the migration to the external stacktrace-js library, the tests were
updated to reference their node_module version. This will ensure for both
stacktrace-js and Fiber we are referencing the proper version that is being
built with during our unit tests.

Fixes #301
fix (Executor): Fixes error reporting for PhantomJS

After fixing the stacktrace normalization, the PhantomJS output needed to be
accounted for when using pure stacktrace-js. The solution was to capture and
handle the normalized stacktrace-js output with a regex. Combines with the
previous push as part of #302 to ensure all tests are passing in automation.
Merge pull request #302 from Jakobo/stacktrace-js

fix (Executor): Improves stacktrace-js integration