Fixed spellings, updated self-update URL and other URLs

Changes:
1. Tutorial.py: Corrected spelling of fiducial and measurable.
2. Shell.py: Updated self-update URL to  https://github.com/sightmachine/SimpleCV/zipball/master, corrected spelling of concise. Also updated updated URL of help page and examples page to the direct URL. Example: http://help.simplecv.org (which redirects) was updated to http://help.simplecv.org/questions/ and http://examples.simplecv.org was updated to http://examples.simplecv.org/en/latest/ .
3. Example.py: Fixed spelling of occurred.