Create Class for Interval Tree based on Region

[dridk]

We can create a class, which can find region overlapping.
For instance, I have a RegionList containing several Region ( chromosom, start, end ) .
Let's do the methods :
RegionList::overlapping(chromsom, start, end) which returns RegionList overlapping start and end.

Note:
Tabix do the same, but work only of bgzip file. This is not the case here. We only do from memory.