Deal with common issues

[spficklin]

It's easy to make the following mistakes that don't cause problems for FUNC-E but cause it to not work and not give any errors messages:

1. The feature IDs in the background, query or terms2feature files don't match. For example, gene IDs, protein IDs or transcript IDs may be used interchangeably but aren't exactly the same.
2. The files may not be tab delimited, but may be space delimited or any combination of white spaces.