Can submit partial data

[mjkraner]

If I enter a start time for sleep but not an end time, and I select an alertness level and hit graph my data -- my data is graphed on the chart.

OR

If I don't enter anything for time at all and just select alertness level and click graph my data, my data is graphed on the chart.

It should not take my data until both start and end time is submitted

Related to #8

[kszatmary]

It is possible to only enter sleep time (both bedtime and wake up), select no alertness level and graph the sleep data only.

[mjkraner]

This is still an issue -- need to reopen it to have devs work on it -- with the new design in place it seems you can enter partial data again and graph.