Remove deriving 'Data', as 'Scientific' is no instance of 'Data'.
Use fast 'encodeUtf8BuilderEscaped' if possible

- only use it when compiling against bytestring >= 0.10.4.0
- speed improvement over bytestring-via-text encoding:
    factor 1.5 - 1.6 for japanase and english JSON messages
    factor 2         for integer encoding

- equal speed for encoding floats
Merge pull request #172 from meiersi/feat-encode-via-bytestring-builder

Feat encode via bytestring builder