flesh out hdf5 backend, adding storage of frequency data and images
load frequency images and data from HDF5 file instead of bin file
bump minimum required pytables version to '3.0.0' so we can use the new_api
update tests to import+read instead of reading directly from bin file
catching AttributeError hides underlying errors that are not related to version
so use an explicit hasattr check for testing version
drop filesize check; listNodes is sufficient
fall back to pytables 2.x API
pep8
share instance of survey_task with SurveyLinePane and delegate survey to the survey_task
replace Delegate -> DelegatesTo; apparently Delegate is deprecated
Merge pull request #31 from twdb/feature/read-images-from-hdf5

Add frequency images/dicts to hdf5 file