Directing NLME7 stdout and stderr to files

New files in output directory: stdout.txt and stderr.txt
Record data moved out of global scope.
Model.__setattr__ ignores private variables.
Model.__setattr__ and Model.Record.__setattr__ transparently convert
values to strings.
Removed literals in Model._nlme_options
Fixed bug in Model._nlme_options involving aliases
Removing Model.summarize while working on it
Setup.py only asks for input on build command

Run setup.py build install now to specify non-default install paths.
Collecting stdout, stderr, and return codes of every subprocess.
Improved error handling in nlme.
Removed ModelError exception.