remove tableAndTreeMatch check when creating a TreeHeatmap

This change removes the constraint that a table must have a row for
each leaf node of the tree.  Without this constraint, the vtkTreeHeatmapItem
can be used to display incomplete datasets.  The item also seems to
gracefully handle the case where the table & the tree have nothing to
do with each other.
Merge branch 'fuzzy_tree_table_match'

* fuzzy_tree_table_match:
  remove tableAndTreeMatch check when creating a TreeHeatmap
Handle the lack of unistd.h on Visual Studio

Use CMake's CheckIncludeFile module to test if unistd.h
is available, and only attempt to include it if so.
Merge branch 'cross_platform_unistd'

* cross_platform_unistd:
  Handle the lack of unistd.h on Visual Studio
Merge branch 'master' of git://visomics.org/visomics