geom_density_tern example not working as expected

[Dario Romagnoli]

Using the example code produces a warning and the plot is different from what expected.

data('Feldspar')
ggtern(Feldspar,aes(Ab,An,Or)) + 
    geom_density_tern(aes(color=..level..),bins=5) +
    geom_point()

#!r

Warning message:
stat_density_tern: You have not specified a below-detection-limit (bdl) value (Ref. 'bdl' and 'bdl.val' arguments in ?stat_density_tern). Presently you have 6x value/s below a detection limit of 0.010, which acounts for 15.000% of your data. Density values at fringes may appear abnormally high attributed to the mathematics of the ILR transformation. 
You can either:
1. Ignore this warning,
2. Set the bdl value appropriately so that fringe values are omitted from the ILR calculation, or
3. Accept the high density values if they exist, and manually set the 'breaks' argument 
   so that the countours at lower densities are represented appropriately. 

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