added ..Rcheck to .gitignore
added corMethod to ggally_cor
all cor fns are now cor_fn to use same parameters
added na.rm to all min/max/range commands
only remove rows if corUse is 'complete.obs'. Set default corUse to 'complete.obs'
added parameter matching and more cases for the removing warning
fixed corUse being an integer and not a value
changed the ddply command to not rely on eval within ggally_cor
make the cordf labels have the correct level order
Merge branch 'cor_method' into dev_cor_method

* cor_method:
  make the cordf labels have the correct level order
  changed the ddply command to not rely on eval within ggally_cor
  fixed corUse being an integer and not a value
  added parameter matching and more cases for the removing warning
  only remove rows if corUse is 'complete.obs'. Set default corUse to 'complete.obs'
  added na.rm to all min/max/range commands
  all cor fns are now cor_fn to use same parameters
  added corMethod to ggally_cor
  added ..Rcheck to .gitignore
documentation