add test for wrong # of units with complex data
tick version
massive simplification of interface
group and file creation functions set creation order tracking on
continued simplification of interface
set_attributes now allows uppercase letters and doesn't coerce to numpy arrays, as this
seems to be working okay in h5py as of 2.2
add entry_time function to directly extract timestamp as float from entry
handle numpy types for sampling rate, append_data returns if data is empty
add overwrite flag back to set_attributes
Merge birdsong:src/arf