Sporadic unit test

[hickford]

Serialisation unit test fails sporadically https://travis-ci.org/tyler/trie/jobs/20983885#L182

  1) Trie save/read when I save the populated trie to disk should contain the same data when reading from disk
     Failure/Error: trie2.get('omgwtflolbbq').should == 123
       expected: 123
            got: 3581127210813096059 (using ==)
     # ./spec/trie_spec.rb:156:in `block (4 levels) in <top (required)>'