0.7-beta port

stable iOS port of nanomsg 0.7-beta

• finished efd cleanup: nanomsg poll and select fully supported on iOS
• updated the repo license to MIT
• wrote some examples in the examples branch
• start using a semver style to match upstream version MINOR
• any new important tags tracked at semver PATCH if upstream MINOR doesn't change

0.5-beta port

ios/osx port of the 0.5 beta release