Compare YANG module revisions

This version of yangdiff supports YANG as defined in 'draft-ietf-netmod-yang-10.txt'.
File names must be in one of these forms:

• modulename.yang (foo.yang)
• modulename@revision-date.yang (foo@2009-03-17.yang)

Modules that are listed on Netconf Central do not need to be uploaded for module validation, but if a different version is uploaded, it will be used instead.