comment on what num_state_vars is in LensAgent init
set_state is an interface for all agent types, added to base agent class
Lens agent starts with an empty list of predecessors
consistent interface for set_state; also will check if input matches len(state)
comments for what _list_to_str_delim does
comment that python reads file lines starting from 0
will return list of floats instead of list of string of floats
explicitely declare default update implementation
changed relative file path (this may have to be coded so it is a parameter)
refactor: function that returns contents as a StringIO before writing to .ex
this also makes the string that will be writtein to file unit testable
made section headers 79 characters wide
test base agent set state -- it will return an exception
unit tests for LensAgent