WIP: Roadmap to 1.0

[mkitti]

I would like to start working towards a 1.0 release of this package. There is a lot of work to do, but it is time to start enumerating what needs to be done to get there.

• Change README.md to give a usage synposis rather than a performance comparison
• List dependent libraries
• Document and ensure a consistent API across all interpolation types
• Improve short-hand syntax
• Document how interpolate should be extended by other packages.

[rick2047]

Just a suggestion, we should also enumerate which other libraries we are going to provide functionality too. Like diffimages discussion which is on going.