Merge pull request #1 from jonahwilliams/fix_win_lookup

fix win lookup of impellerc, fix type error in json decode.

mention related shader_uniforms project in README

update pubspec

use new impellerc feature to parse frag files

add activate command to Getting Started

added example

flesh out the GPU data types and start looking at impellerc integration

package cleanup

simpler direct access to vec/mat fields and an offset bug fix for mat4

doc comments and license headers

more typos

typos

readme

make script runnable using 'dart run', provide option to override output dir