752 - Formatters are now simple functions

752 - Formatters are now simple functions
onlyShowUnchanged param and dependency fixing
si -> siSuffix
Removing onlyShowUnchanged var from siSuffix
Fixing API breakage in quicktests for formatter

Close #752.
We should define a type for the formatting function, so the JSDoc can be clearer. ex:
```
export interface Formatter {
  (d: any): string;
}
```
Then the TSDoc can list this as returning a `Formatter` and not just a `function`.