cell body expansion

cell body is now saved (and read) as array of strings to support
diff-ing models
Merge branch 'master' into ildipo/jsonformat
do not copy default notebook
transform only cell body
Merge pull request #783 from twosigma/ildipo/filesearchdirs

added file search dirs for notebook load
Merge pull request #775 from twosigma/ildipo/jsonformat

Ildipo/jsonformat
Merge pull request #779 from twosigma/ildipo/issue-100

do not copy default notebook
disable running tests since they do not work
Merge pull request #784 from twosigma/spot/766

disable running tests since they do not work
Merge branch 'master' into ildipo/filesearchdirs