bugfix: call `setInstanceFollowRedirects` instead of `setFollowRedirects`
bugfix: call `setInstanceFollowRedirects` instead of `setFollowRedirects`

the latter is a static method operating on the class itself, and thus
might lead to unwanted results with concurrent instances.

ringo/ringojs,ringo/ringojs,ringo/ringojs,ringo/ringojs