Modularised library code into smaller files

Each of the filters have been placed in their own category, with each category comprising a JS file, named as follows:

• noise_generators
• line_generators
• brightness_adjs
• colour_tints
• offset_filters
• specks_generators

Each of these files contain their respective filter functions, and can be found in the lib dir.

70 image filters; compatible with both the browser & NodeJS

Currently contains over 70 image filters, including the following filters and effects:

• sepia
• greyscale
• solange effects
• inversion
• retro effects
• noise generation
• tinting

This release is compatible with both the browser and NodeJS, however NodeJS version only contains the filterImgData method, as the canvas rendering functionality implemented in Node by the developer may differ.

Full usage notes, sample code and demos can be found at: https://silvia-odwyer.github.io/pixels.js/