Dino dex

Refactored code and cleaned up arrowheads following discussion with Dan
1. refactor lines 32-38 into their own method
2. your filter terms and the associated method calls tend to match (`is_biped?` -> `filter == "biped"`, `is_fat?` -> `filter == "fat"`, etc), so you should be able to determine what method to call based on the value of `filter` alone, instead of having to do these explicit checks + mappings. take a look at [Object#send](http://ruby-doc.org/core-2.1.5/Object.html#method-i-send) and/or [Module#define_method](http://ruby-doc.org/core-2.1.5/Module.html#method-i-define_method).