Add new roclets: depends_roclet in roclet-depends.R and index_roclet in roclet-index.R
Also alter roc_output.namespace function in roclet-namespace.R so that Import field is updated in DESCRIPTION.
Update DESCRIPTION and NAMESPACE files, and added INDEX file to reflect changes of previous commit.
Add documentation for depends_roclet and index_roclet
Merge remote-tracking branch 'vapniks/master' into develop