Fix copyright in documentation for built files

referring to #68 and https://github.com/SciTools/iris/issues/636

Used a variant of the below command:
`find . -type f -exec sed -i 's/2010 - 2012/2010 - 2013/g' {} \;`

This fixes the scitools built documentation exclusively, not the iris source code from which this build originates.  The reason for this is that we cannot now change the iris tag release, in order to generate corrected build documentation.