"SimpleTrie" is a naive implementation of "Trie".
"(SimpleTrie)._childSeq" stores child nodes.
"Descend a trie and find the node corresponding to "key".
"(SimpleTrie).search" succeeds if all bytes of "key" are read.
Remove a needless import statement.
"(SimpleTrie).insert" creates new path to the node correspoding to "key" if the path doesn't exist.
Replace "Undefined" with "null".
"Trie" has an arbitary int "value" instead of "id".
Merge branch 'feature/trie-simple'