new function cutpat

A function “cutpat” which returns a pattern containing only events
within the specified part of a cycle.  I find this useful for applying
functions to parts of patterns; a shortcut example for this is the
function “within”.
Update Pattern.hs
add mapCycle
move some things from Strategies.hs to Pattern.hs
- use splitQueries to generalise splitting queries at cycle boundaries
- add scan
- make "density 0" transformation return silence
- bugfix densityGap
- add seqP (and helper functions playFor, playWhen and whenT) for linear sequencing of patterns
- add fadeOut and fadeIn
- move spread, slowspread, whenmod, superimpose, trunc and spread' from Strategies.hs
- add within (and helper functions zoom, compress and sliceArc)
Merge pull request #38 from bgold-cosmos/patch-1

new function cutpat
Merge branch 'master' of https://github.com/yaxu/Tidal

Conflicts:
	Sound/Tidal/Pattern.hs
remove git conflict chevrons
rename within to withArc, and add revArc
remember to wrap zoom in splitQueries