Minor update to make PMap use trie directly instead of PVector
Minor update to make PMap use trie directly instead of PVector

jml/pyrsistent,tobgu/pyrsistent,jml/pyrsistent,jml/pyrsistent,tobgu/pyrsistent,jkbjh/pyrsistent,Futrell/pyrsistent,jkbjh/pyrsistent,tobgu/pyrsistent,jkbjh/pyrsistent,Futrell/pyrsistent,Futrell/pyrsistent