Addressed issue #127.

See new get_int method.
Fixed bug in get_int (thanks Travis for reporting the bug).
Optimized get_int by adding exit condition.
Adjusted sd_vector test to capture special case.
Initialization is out of bounds.
Simplified code.
Implemented get_int for remaining bitvectors.
Merge pull request #128 from simongog/bv_access

Addressed issue #127 for all bitvectors.