added string and FSeq input handling to guess_type
made guess_type ignore case and gaps
guess_type returns 'illegal' if 'U' and 'T' in a sequence
in guess_type set ambiguous if only one or two [ACGT]
added tests of utility functions
fixed exit codes
improved error handling and edge casing in FSeqGenerator
added FSeqGenerator tests
release 1.11.1