Added configurable ignore feature for files and folders, added additiona...

...l files to default ignored

##### Completed:
* Added the two requested files, as well as two other OS generated files I see quite frequently on Mac to the default ignored files
* Added ability to add files and folders to ignore through config.json
* Updated README.md and Getting Started > Configuration, added item for "Ignore"

##### Todo:
* Add support for wildcards
* Add support for paths