Blacklist for skipping tests or test folders in different environments.

This is a possible feature for ticket #107;  It adds the ability to skip tests based upon the following blacklist in the settings.json:

```
"test_settings" : {
    "default" : {
        ...
        "blacklist" : {
              "files" : ["widgets/file1"],
              "directories" : ["pages", "templates"]
        },
    "env2" : {
        ...
        "blacklist" : {
              "files" : ["widgets/file3"],
              "directories" : ["pages", "registration"]
        }
    }
}
```