scientific-0.3.4.2: Numbers represented using scientific notation

# scientific-0.3.4.2: Numbers represented using scientific notation

`Data.Scientific` provides the number type `Scientific`. Scientific numbers are arbitrary precision and space efficient. They are represented using scientific notation. The implementation uses a coefficient `c :: `Integer`` and a base-10 exponent `e :: `Int``. A scientific number corresponds to the `Fractional` number: ``fromInteger` c * 10 `^^` e`.

Note that since we're using an `Int` to represent the exponent these numbers aren't truly arbitrary precision. I intend to change the type of the exponent to `Integer` in a future release.

The main application of `Scientific` is to be used as the target of parsing arbitrary precision numbers coming from an untrusted source. The advantages over using `Rational` for this are that:

- A `Scientific` is more efficient to construct. Rational numbers need to be constructed using `%` which has to compute the `gcd` of the `numerator` and `denominator`.
- `Scientific` is safe against numbers with huge exponents. For example: `1e1000000000 :: `Rational`` will fill up all space and crash your program. Scientific works as expected:

    > read "1e1000000000" :: Scientific
    1.0e1000000000

- Also, the space usage of converting scientific numbers with huge exponents to ``Integral`s` (like: `Int`) or ``RealFloat`s` (like: `Double` or `Float`) will always be bounded by the target type.

Modules

- Data
  - ByteString
    - Builder
      - Data.ByteString.Builder.Scientific
  - Data.Scientific
  - Text
    - Lazy
      - Builder
        - Data.Text.Lazy.Builder.Scientific