Enhancement #85. Enhance UA.contact.toString logic. Thanks @wakamoleguy
Fix #190. Allow defining an empty Stun Server Set. Thanks @dpocock
Fix #193. Do not reference extraHeaders parameter, but clone it instead

to avoid header duplication when apps use a global variable
#190. Modifiy remaining extraHeaders reference
Improve 'hostname' parsing (fix #196).
Merge branch 'develop' of github.com:versatica/JsSIP into develop
Update for v0.4.0.20140212.1