Cfn-lint

Features
- Added a rule to check for only one resource property in a set
- Added a rule for more than one of resource properties in a set
- Added a rule for mutually exclusive resource properties

Fixes
- Support parsing JSON files that have tabs
- Better error handling for when a property is a list instead of an object
- Error handling for when files can't be read or don't exist

Features
- Fix for supporting more parameter types when checking REFs to parameters for Security Groups

Features
- Exit code non zero on errors or warnings

Features
- Testing CloudFormation resources against the Resource Spec
- Test Functions against supported included functions
- Test overall CloudFormation structure
- Test Regionalization of a template against the Resource Spec
- Ability to add additional rules on parameter
- In depth checks of values around AWS::EC2::VPC, AWS::EC2::Subnet, and AWS::EC2::SecurityGroup