ENH: Extending TrialHandler's n-back information options

In response to user query at
<https://groups.google.com/forum/#!topic/psychopy-users/9aeU1AgEJv4>.
Sometimes access is needed to information from previous trials (as in
an n-back task). As a kludge, the trialHandler's getFutureTrial()
function could be used for this by passing a negative index value, but
as it wasn't designed for this, it didn't include a bounds check to
handle trying to access a trial before the first one. This has now been
added.
To be explicit, have also added a getEarlierTrial() function, which
simply calls the getFutureTrial function but ensures the index is
negative.
Merge pull request #338 from m-macaskill/master

	ENH: Extending TrialHandler's n-back information options
DOC: Fix for namespace issues in psychopy.data API examples

A user found problems when trying to create a Multistairhandler:
<https://groups.google.com/forum/#!topic/psychopy-users/kPEtdAp5C_s>

This was due to the docs not specifying that handler classes are
instantiated with a "data" namespace prefix. Fixed this to make all of
the examples in the comments consistent (previously the correct syntax
was given only for one QuestHandler example).
Merge pull request #342 from m-macaskill/master

DOC: Fix for namespace issues in psychopy.data API examples
DOCS: updated workshop details
Merge branch 'master' of github.com:psychopy/psychopy
ENH: first attempt at adding Static Component

Done:
  - component has been created
  - renders in the Routine using a red box (no separate row)
  - Settings Component now writes script code to get current frame rate (needed by static)
ENH: code components now use a separate type of param val type = 'extendedCode'

It means we don't have to check for a list of param names to see which
are this format.
ENH: added Static component icon and code
ENH: Static Component now based on core.StaticPeriod class

also improved rendering of it in the Builder view
ENH: we don't always need the icons for the components so make it optional to fetch

added test for StaticPeriod
ENH: added documentation for static period/component and create one by default
BF: fixed problem with images appearing grey when set 'every repeat' or 'every frame'

Was caused by the fact that the image was created using a luminance sine wave
and then switched to being an rgb bitmap which needs a different shader
program
Merge pull request #339 from jeremygray/master

RF: BufferImageStim tweak; sound file compression
ENH + DOC: microphone compression + changelogs, docs