Add parameters for the transformation used to produce the canon

This will allow to use the same canon() function with different
transformations.
Create note using textual notation instead of numeric indexes

Note(2,4) is equivalent to Note("D,") which is more explicit.
Add canon generated by transposition
Add canon generated by retrograde
Add canon generated by rotation
Add canon generated by repetition twice faster
Update pyknon to latest upstream version

This fixes a typo on noteSeq.stretch_interval() method.