No default hash values in CallIndex

because it creates unnecessary values when searching
the index for keys that don't exist yet

Cleanup of CheckSQL because of the F rating in code climate

Report controllers again for -m and -d

 - Removed brackets where possible.
 - No more assignments in if-statements
 - Refactored out unsafe argument array checking

 - CVE checking is now a simple hash
 - Removed implicit returns
 - Removed duplicate code from find_scope_calls
 - Removed assignments from if statements
 - Bracketed ambiguos statements
 - Onelined simple if statements 

Don't report immediate XSS dupes as weak warnings

Refactor report generation code into separate classes for different formats

Add right value to results in XSS check

Relax slim dependency for Slim 2.0.0

User exit code of "1" when path is not a Rails app

Limit branched value depth, add --branch-limit option

Add more methods to check for command injection

should have been a test that the warning does _not_ appear.

closes #206 finally

Fix output format detection to be more strict again

Allow empty Brakeman config file

and also -f should override detection