fix handling of query sequences with FASTA comments (ete2 SeqGroup used tab as comment separator in FASTA desc line, whereas hmmer used space - which led to confusion. Now space is used everywhere. Unfortunately ete2 had to be patched to achieve this, but it wasn't the first patch anyway.)
- move taxonomy assignment code into classfy_util.TaxClassifyHelper, which is now called by both epa_classifier and find_mislabels
- do no rely on rank names being unique; use full taxonomic path as rank identifier instead
- import epa_2_ptp only if needed (if --ptp specified) to avoid nasty SciPy dependancy for non-ptp runs
- some minor cosmetic changes in classifier output generation