simplify len()
fixed a bug that was accidentally seeking wrongly in the file
added flush() method
Added two-dimensional indexing
updated version number

This release includes quite a few new features and bug fixes:
- a flush() method
- fixed bug that reported the wrong len()
- indexing now works for frames and channels
- read() reads to the end of the file by default
- fixed bug that seeked to the wrong place in some cases.

A big thanks to @mgeier, who helped to find and fix a lot of these issues!
fixed links in README