Add a :headers option to invite
Omit the extra newline if there are no headers passed to #invite
Move headers to the end of the SIP INVITE
Remove debugging #p call from scenario_spec
Merge branch 'master' of github.com:mojolingo/sippy_cup into feature/headers
Update doc generation comments to include :headers option
Re-add specs for :invite option
Fix duplicate line and doc newline issue
Fix broken specs
Revert "Fix broken specs"

This reverts commit 89b0721f99f8117c3de187f8f921ff8f3289e601.

The specs were not broken, the implementation is.
Fix excessive newlines in INVITES

Sent messages should never have leading whitespace since this confuses specs and makes implementation more difficult