CmpH5Reader: fix for bug opening non-existent file

Attempting to open a nonexistent cmp.h5 file ran into an infinite loop
in Python's cyclic garbage collector.  See:

   http://bugs.python.org/issue10794

... which has been sitting in the bug tracker without resolution for a
very long time.  The quality of the CPython interpreter continues to
unimpress us...

The removal of __del__ should be harmless and seems to remedy the
problem.

[Tracking bug 21562]

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 119444]
Add basic tests for readsInRange

[Tracking bug 21562]

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 119460]
setup.py: require Python 2.7

[Tracking bug 21562]

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 119570]
rangeQueries: fix indexing convention to be 0-based, end-exclusive

This brings the coordinate system of rangeQueries in line with the
coordinate system conventions of our cmp.h5 files, as well as the
familiar conventions of Python and the C++ STL.

So for example, the query for interval [0, 5) now returns reads
overlapping (zero-based) reference positions {0, 1, 2, 3, 4}.

Note that this also changes the dimension of the return value of
getCoverageInRange to (queryEnd - queryStart, 1)

This fixes bug 21232.

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 119571]