DataBook read issue

[nasa-ddalle]

Follow-on to #18

From @rbreslavsky:

One more comment on this. The databooks are all generated correctly now. However, when they are read back in (for carpet plots or other operations), lists of strings get split up into multiple parts. So for instance, if I have "['hvanleer', 'hvanleer']" in a cell, that gets split into two parts by util.split_line().