fixing warnings
fixing static analyzer errors
Better error handling

Creates a custom error if we detect not enough information to perform migration.

Also, don't override error if we already set it.
Errors by reference

As a caller of this method in the parent app, I would like to inspect the error in more detail.
travis testing
travis testing
Merge pull request #130 from jcarroll3/warningsAndStaticAnalyzerFixes

Warnings and static analyzer fixes
Merge pull request #131 from jcarroll3/createCustomError

Better error handling
Merge pull request #132 from jcarroll3/errorsByReference

Errors by reference