Added two optional parameters to the XAB plugin so that they key that
subjects press to answer left/right is a parameter. The parameters have
default values of 'q' and 'p' to maintain compatibility.
The top level object is jsPsych, and plugins are defined as jsPsych.PLUGIN.
The library also loads everything dynamically now, so the user only needs to load the main jsPsych script (and specify the src for any plugins).
This also changes how the library is loaded initially, since it is not based on the jQuery method anymore. See wiki.
Plugins now have a consistent internal structure, with better variable scoping.
This version breaks backward compatibility due to a change in the syntax of how experiment objects are declared.
-- added time recording to samedifferent task, which records the actual clock time
that stimuli were onscreen. We're using this data to verify that stimuli are
presented for the desired amount of time.
-- fixed a bug in XAB task, where some correct responses were not being recorded.
