Rename BuildFrom.fromSpecificIterable to fromSpecific

[szeiger]

...and use Iterable instead of IterableOnce as the parameter type. The current version is useless for compatibility.

[szeiger]

But BuildFrom is a trait so we cannot just add the correct method without breaking binary compatibility. So much for that...

[szeiger]

Another option would be to keep the broken interface and add an extension method. It doesn't help for implementing BuildFrom but you cannot implement Factory in a cross-compatible version, either.

[szeiger]

Fixed in #200