split diff per file
introduce DiffsController
remove diff action from files controller
split diff computation into many small functions
add specs on DiffsController
add spaces around assignment operator
shorten line
clean the code, fix diff of first commit retrieval
Merge branch 'staging' into 865-introduce-diffs-controller
Merge pull request #1055 from ontohub/865-introduce-diffs-controller

865 introduce diffs controller
change fixture_file ontology-call to ontology_file.
Merge pull request #1112 from ontohub/fix_fixture_calls

change fixture_file ontology-call to ontology_file.
deactivate the hound-checker for multiline-lambda

As we want to use the 1.9 syntax (->(args)) for every lambda,
whether it is single-line or multi-line, we'll need to deactivate
the check, as it can't be configured.