Check the ref span in slices #78
Description
Each slice has a start and span (ie start to end) indicating the
portion of the reference covered by data within that slice.
However the Java code appears to compute this incorrectly using the
start coordinate of the first and last sequence not the rightmost
base.
....
The first read starts as pos 1.
So that implies reference coverage from 1 to 2687 inclusive, not 1 to
2618 as the header indicates. This is causing bugs now in my
cram_to_sam convertor due to loading the reference on demand per
slice.