If tree imports successfully, add supporting file.

This copies the input text (whether an uploaded file or pasted into a
form field) to a new file in the supporting-files area for this study,
so that it can be reviewed, downloaded, and deleted from within the
curation app. Fixes #418.

NOTE that this is in addition to the saving of input data to peyotl's
scratch folders. The latter is for diagnostic purposes.
os directly from os import instead of shutil
Merge branch 'master' into supporting-files-from-imported-trees
Merge pull request #476 from OpenTreeOfLife/supporting-files-from-imported-trees

Supporting files from imported trees