PEP8 and fix various flake8 warnings
added THANKS.txt
Merge pull request #73 from sciunto/pep8

PEP8 and fix various flake8 warnings
candidate fix for confidence_intervals() and copy_params_on_output
avoid divide by 0 messages
change "dict comprehension" to python2.6 compatibility
Merge branch 'master' of github.com:lmfit/lmfit-py into run-tests-on-travis