env.float doesn't work with negative numbers

[kszilagyiOT]

Negative numbers are converted into positive ones. env.list seem to work with subcast I think the problem is here, the minus sign is stripped: https://github.com/rconradharris/envparse/blob/e67e70307af19d925e194b2a163e0608dae7eb55/envparse.py#L132