Fix memory leak from bam_plp_init.
Fix leak from the Tabixfile index.
Fix leak from kseq_init when opening gzipped files.
Fix leak from ks_init in tabix_file_iterator.
Fix leak from malloc in tabix_generic_iterator.__next__
Fix leak in TabixIterator kstring.
Fix leak from unclosed gzdopen ins tabix_file_iterator.
Merge pull request #56 from mckinsel/leaks

Fix memory memory leaks in tabix files and IteratorColumn.