Analyze Scripts not in a Gem

[rameshvarun]

Currently we only analyze scripts that are part of gems. This PR adds code to the scanner that puts all loose scripts in their own source unit.

[sqs]

• [x] See if this breaks any popular projects:
  • [x] Ruby stdlib
  • [x] Rails

Does this change the output on projects that don't have stray files?

[sqs]

All the code looks great to me. Just added a few comments.