fixed input_units in read function
added scratch directory for downloaded or generated data files
Updated chile2010 example to use new dtopotools and to download and generate files in scratch directory
Merge remote-tracking branch 'rjleveque/dtopotools2' into dtopotools2

* rjleveque/dtopotools2:
  Tests all work, new IO test for dtopo added
  Raise nose.SkipTest if scipy not installed
  Add documenation and fix bugs
  Add old dtopotools class structure for reference
  Merge newest changes with various bug-fixes
modify verbose message
change SCRATCH to scratch