Fix up some string concatenation, line length issues, etc. by mulhod · Pull Request #645

Fix up some string concatenation, line length issues, etc. by mulhod · Pull Request #645 · EducationalTestingService/skll

Closes #636

Mainly, this PR has to do with cleaning up some multi-line string concatenations (or removing them altogether when possible). There are a couple other randomish improvements I made as well (like reducing the length of some very long lines or lines where it was easy to do, removing unused parameters from a function used by a test, etc.).