Fix for "1.".to_yaml (#109)

Potential fix for #109

Seems to have no performance impact on jruby

    > Benchmark.measure { 10000000.times { "2352352352352352.".end_with?('.') }}
      1.540000   0.060000   1.600000 (  1.557000)
    > Benchmark.measure { 10000000.times { "2352352352352352." == '.' }}
      1.570000   0.080000   1.650000 (  1.536000)