s/possibilities/opportunities
Add section 04 of tutorial - changing synths
Display the Sonic Pi logo in empty doc windows
rename tutorial 04 to switching synths
Add section 05 of tutorial - stretching and compressing samples
minor tutorial tweaks
unify synth defaults:

* an attack of 0, 
* a decay of 0,
* a sustain of 0,
* a release of 1
* mod_phase of 0.25 (for mod synths)
tweak tutorial
reduce emphasis noise!
Add section 6 - durations with envelopes including lots of nice diagrams
minor tweaks to envelope tutorial section
renumber tutorials 05 and 06 ad beef up envelope section a little
add a new section on amplitude
update tutorial
Upgrade mono and stereo sample players to ADSR envelopes :-)
Add tutorial section 08 - enveloped samples
Fix speling mistakes in tuturial
Default all envelopes to exponential curves between segments:

* Also add new param env_curve which allows the user to specify one of
  the other curve types. linear, exponential, sine, welch, squared, and 
  cubed
Add tutorial section 09 on playing sub parts of samples
add more information on panning to the parameters section of the tutorial