Merge pull request #467 from PyBossa/generalise-presenters

make presenters list configurable
Remove not used modules. Refs #469
PEP-8 Compliant
Rename the importer to CSV. Closes #469
Update the unit tests. Refs #469
PEP-8 Compliant plus some fixes. Refs #469

This commit finally fixes the PEP-8 style, and moves the Mock to the new
importers.py file.
Add Google Drive Spreadsheet importer. Closes #470
Remove a print method. Refs #470
Use a two-column grid approach. Closes #471
Update documentation for latest changes.
add copyright boilerplate