Venom Fixes

Cleans up Scorpion & Toad text, kinda brings back the Viper Combo, and
cleans it up.  Now all we're missing is Lizard and we'll deal with that
once the new system comes out.

Thanks for making this both accessible and robust, swwu.
Merge branch 'master' of https://github.com/CleverRaven/Cataclysm-DDA