[Fix #1350] Check that Blocks cop doesn't create syntax errors

The cops AndOr and Not share the same logic, but it looks like
their autocorrect methods are not capable of introducing syntax
errors.
Fix spelling error in spec
Merge pull request #1377 from jonas054/1350_autocorrect_blocks

[Fix #1350] Check that Blocks cop doesn't create syntax errors
[Fix #1374] Always auto-correct one cop at a time

The only way to guarantee that two cops don't destroy
the code by doing simultaneous changes, is to save
the file after letting one cop to its corrections, and
then parse it again before doing any more corrections.