TTS: Pass molecule parsing error up to the user

[mattwelborn]

For example, "h2o" is not a valid chemical formula. This gives "Please enter required fields with valid values." if no predictions have been made before, or the previous prediction if a prediction has been made before.

I think we should give the user a message that says "Your molecule string could not be parsed. Don't forget to capitalize element symbols!"

[dgasmith]

We should try to get a valid input by using by:

1. Upper case everything
2. Title case based on string split

[mattwelborn]

2. is a little tricky. Does naf == "NaF" or "NAf"? I know "Af" is not a legit chemical symbol, but now we have to try all the possibilities and compare against the periodic table.

[mattwelborn]

Similar issue with 1. "ni" == "NI" or "Ni"?

[dgasmith]

Something wacky I think:

formula = None
try:
    formula = parse_formula(string)
except:
    pass

if formula is None:
    try:
        formula = parse_formula(string.upper())
    except:
        pass

Not sure of a better control flow.

funcs = [lambda x: x, lambda x: x.upper(), lambda x: "".join(x.title() for x in num_split)]

for func in funcs:
    try:
        formula = parse_formula(string)
        break
     except:
        pass

[dgasmith]

I do want to come up with something clever in the future, but something to get over silly h20 errors. Everyone only cares about CHNOPS anyways right :)