Resolve the overload in GitHubScanner methods fetch

[sofiabobadilla]

Link to the class GitHubScanner

methods fetch(long startTime, long endTime, FetchMode fetchMode, Set<String> repos) and fetch(FetchMode fetchMode, Set<String> repos) shouldn't share the name and should be documented.

Why overloading doesn't support the SOLID principle Open/Closed?

[sofiabobadilla]

FYI I can't assigned myself, but I'm working on it