refactor freshen-fixtures task for readability.
extract hets-cmdline-options into config.
freshen fixtures only when necessary

'Necessary' is being determined by the modified timestamp of the
hets-binary (or wrapper-script) in relation to the xml-file which is to
be produced.
add freshen-task to default rake-task

And rely on this task when running travis, again.
fix default rake task

The default rake-task comes with spec and cucumber as dependencies. If
we provide more we just append to this list. So we'll clean the
prerequisites of those tasks beforehand.
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.
GitRepo refactorings: more delegates, url -> path.
Delegate empty? method.
Use ref instead of r as block variable name.
Use '/' as default path.
Simplify path_exists method.
Merge pull request #1103 from ontohub/fix_hound_for_lambdas

deactivate the hound-checker for multiline-lambda
Merge pull request #1096 from ontohub/freshen_fixtures_only_when_necessary

Freshen fixtures only when necessary
Do what the hound says.
Merge pull request #1074 from ontohub/refactor-clean_git_a_little

GitRepository refactoring
add method to check if a repo/onto can be deleted
delete repository asynchronously
Use active scope for retrieving repositories.

I could have introduced a default scope, but this
would result in broken migrations: Some migrations
change existing repositories. They would fail at
selecting repositories because there is no column
'destroying'.

Also default scopes cannot be overridden.
Log destruction of repositories
Remove old mechanics to destroy repositories.

When destroying a repository asynchronously, we
don't need to mark it as destroying in a class
instance variable any more. Instead, we mark it
in the database.