2.0.0

Although the version number might suggest otherwise this is a rather modest
release compared to previous releases.

There are 3 big changes in this release:

1. A refactored and less confusing CLI.
2. The caching system has been removed as it was too problematic.
3. The API used for registering analysis classes has been changed to make it
   easier to register custom classes.

The first change is not backwards compatible with previous releases of
ruby-lint, hence the mayor version increase.

The following other changes are included in this release:

• Fuzzy file matching when scanning for external files has been removed. This
  was too problematic and would cause problems such as
  https://github.com/YorickPeterse/ruby-lint/issues/105.
• Definitions for Minitest have been added.
• Proper handling of methods called on block return values.
• Constant paths with variables in them are handled properly.
• Diagnostics emitted by the parser Gem are re-used properly by ruby-lint
  instead of always being displayed as errors.
• ARGF is handled with extra care so that ruby-lint doesn't throw tons of false
  positives.
• Debug output has been removed from the CLI, it will be replaced with a better
  system in the near future.