More color matching functions.

I was looking into implementing the color vision deficiency simulation that @m-lohmann found in #43. That uses the Smith-Pokorny cone fundamentals, which according to [this](http://www.cvrl.org/database/text/cones/sp.htm) page is defined in terms of the Judd-Vos adjusted color matching function.

In this PR I've implemented more a  general purpose color matching function to replace `cie_color_match`, called `colormatch` which works like:

  * `colormatch(λ)`: evaluate CIE 1931 CMF (like `cie_color_match`)
  * `colormatch(CIE1931_CMF, λ)`: evaluate CIE 1931 2-deg CMF (same as `colormatch(λ)`)
  * `colormatch(CIE1964_CMF, λ)`: evaluate CIE 1964 10-deg CMF
  * `colormatch(CIE1931J_CMF, λ)`: Judd's adjustment
  * `colormatch(CIE1964JV_CMF, λ)`: Judd-Voss adjustment

Someone else should sanity check this, since I didn't even know about these other color matching functions before yesterday. I got the data from http://www.cvrl.org/, it's in varying resolution, e.g. the Judd data is 10nm increments. If there's a higher resolution version somewhere, or other important CMFs that should be added, let me know.

![cmf2](https://cloud.githubusercontent.com/assets/210361/3635538/23ce04bc-0f7b-11e4-97d9-b5ea47b32c7f.png)