Fix spelling

Fixes #69

Checks for SpatParams caused errors if parameters weren't supplied in the right
order. Fixed by making setParams a method and reordering the update list
before setting parameters.

Fixes #66

Groups (and paths) were being simulted in alphanumeric rather than number
order. Fixed by making the Group column a factor.

At request of Bioconductor core team

scater normalise renamed to normalize

Fixes #48

Fixes #48

These would sometimes error due to sampling of example dataset

* master:
  Fix group factors bug

From: Luke Zappia <lazappi@users.noreply.github.com>

git-svn-id: file:///home/git/hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/splatter@131740 bc3139a8-67e5-0310-9ffc-ced21a209358

* master:
  Change mean-dropout to mean-zeros
  Add verbose to scDDEstimate

From: Luke Zappia <lazappi@users.noreply.github.com>

git-svn-id: file:///home/git/hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/splatter@131415 bc3139a8-67e5-0310-9ffc-ced21a209358