bugfix

metric name is shown properly, instead of repeating symptom name
update security
proper association between disease:symptom:metric

deletion, rejection if empty, etc
unique IDs for symptoms & metrics

(e.g., fever is fever, regardless of flu or cold)
user symptom submission scaffolding

users greeted by front-end decision tree.  Selecting "I am sick" leads
to a symptom submission form. Symptoms are paired with metrics and
their corresponding values.
symptom and metric find methods

symptoms can be called randomly, by disease, or weight. metrics can be
called by its symptom.

note that the random symptom method is extremely slow and is only used
because there are few symptoms.