Better shibboleth authentication errors

Added an error message when the authentication attribute is missing.
Removed the garbage email address used as a placeholder
Use $identifier as a message placeholder so it is easier to add new
options without more switch statements.
Merge pull request #658 from jrjohnson/657-shibemail

Better shibboleth authentication errors
fixed typo in name of referenced saucelabs cofig file.
numerous style and formatting tweaks. minor content tweaks. various spelling error corrections.
minor formatting tweak

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added code fencing

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formatting fix.

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Merge pull request #659 from stopfstedt/localsauce_readme_tweaks

Localsauce README tweaks