start work on #33

add giflib source and include it binding.gyp
start work on #44 - get pixel
use v8 array as return type for getPixel
validate getPixel arguments. return a color object
add tests for getPixel
add getPixel docs to the readme
register 'color' type with decree, instead of manually validating
start work on #45 - set pixel
add setPixel tests
make normalizeColor assign default alpha value instead of validateColor
add setPixel method to Image and Batch prototypes
Merge branch 'feature/decree-color-type' into feature/set-pixel
fix typo
add coordinates validation to setPixel
Merge branch 'feature/decree-color-type' into feature/get-pixel
add 'interpolation' decree custom type
add 'axes' decree custom type

this commit makes axes case sensitive
add 'image' decree custom type
init prototypes from index.js
add png and jpg params validators