Fix x-ticks in panel c of: gb.plots.plot_behaviour_aggregate

[athms]

Panel c displays p(choose item) ~ (item gaze - max gaze others).

Currently, the ticks can be off for certain gaze distributions, such that the x-axis does not show the full range of (item gaze - max gaze others) from -1 to 1. We should thus set the ticks such that they always reach from -1 to 1.

[moltaire]

The bins in panels a and b of gb.plots.plot_behaviour_aggregate are also bugged:

• The rightmost bin sometimes seems to contain wrong data (e.g., abnormally high RT, abnormally low P(choose best))
• The created bins are sometimes very weird. For a dataset with two items, item values 1-5, it created bins at [0.67, 2.67 and 4.0]:

The value_bins keyword accepts an array, but that array is used for plots a and b, even though they require different bins.