consolidate formating of api data by modifying enroll_data() to take input of pre-formated data rather than raw.
remove function unpack_latest() and unpack_full() and associated test.

change some internal variable names for clarity and revise function comments.
re-write get_and_store() function for clarity.
change internal variable names in extract_data() and rename as extract_all_data()

also change insert value of empty prediction field to None from an empty string u''
move database setup into a function.
add index statements.
rename instances of 'cursor' and 'connection' for clarity and connsistency.
rework tests for db creation and modify tides.py to not actualy initiate a db on its own
add 'recent' to set_querry().  retrieves last three days of data.

move db commit to every loop of insert instead of once at end.  overkill?  I thought i lost some data but in retrospect probably did not.
move commit back to end of enroll() function, test seems to show that it works just fine.

also change parameter in get_and_store() shortcut to 'recent'
alter format_data() to convet timestamp into a datetime and value into a float.

not sure how this will work with database yet...
set up sqlite3 to return timestamp as a datetime object, and the value as a float.

not sure if I set prediction to be a number if i can then use None until I get a value?
set PRIMARY KEY on time in tides table to constrain values to unique.  should probably trap IntegrityError in case we messup.

also added file tdrun.py which is a helper script to step through a few functions.
Merge branch 'get-api-data' of github.com:johnny-lighthouse/tides into get-api-data