Set up exports; move display-oriented functions into display.jl
Convert many algorithms to new framework, and test them

Color-centric utilities still need to be converted

Note that this also adds new algebraic functions and a scaling function.
Update README
Fix conversion to plain array
Update documentation
Tweak docs
Fix doc formatting
Create REQUIRE
Merge pull request #5 from jwmerrill/master

Add a REQUIRE file to pull in dependencies
Tiny doc tweak
Remove Iterators from requirements
Add sRGB classes to classdict in imread.
Merge pull request #6 from jwmerrill/s-types

Add sRGB classes to classdict in imread.
Add filtering example to the documentation
Improvements in scaling and clipping
More utility functions for scaling
Bugfix in display buffer handling; extend scaling during display
Generalize sc() scaling
Document how to add a new image reader
Merge pull request #8 from rsrock/master

Documentation for creating new image readers