bug fix: comparing different file types

fixed bug where out of bounds exception was being thrown when images of
two different file types are compared. this should also correct the
issue where conflicting properties were not being colored properly
bug fix: results page exception
changed path to results

results path now set to /tmp/differ/[username]/results
changed link to documentation

documentation link changed to https://differ.readthedocs.org/en/latest
Merge remote branch 'origin/anonymous_interface'
artefact jdtcore.eclipse excluded from pom.xml - compilation of web application failed because of it