initial stab at exception handling around file operations
Merge branch 'master' of github.com:ged-lab/khmer into feature/missing_file_exceptions

Conflicts:
	lib/counting.cc
added in (untested) file error testing in hashtable load
added test for loading truncated counting hash; results in infinite loop
Merge branch 'tests/file_exceptions' into feature/missing_file_exceptions
test for IOError on attempt to load truncated k-mer table
marked source files that need exception handling for reads
shifted eof into general catch block
Merge branch 'master' into tests/file_exceptions
Merge branch 'master' into feature/missing_file_exceptions
removed highmem attr from truncated file load test
minor cleanup of _khmermodule: use Py_RETURN_NONE
added test for nonexistent file
merged properly with tests
clean up poential free of unallocated objects
added printout of error messages to file tests in test_counting_hash
cleanup of counting hash load function
added hashbits file loading tests
Merge branch 'tests/file_exceptions' into feature/missing_file_exceptions
added better exception handling to load hashbits function