Add xcode8 to Travis CI matrix
Add xcode8 to Travis CI matrix

dgdosen/Nimble,abbeycode/Nimble,DanielAsher/Nimble,AnthonyMDev/Nimble,Quick/Nimble,jeffh/Nimble,jeffh/Nimble,abbeycode/Nimble,twobitlabs/Nimble,abbeycode/Nimble,AnthonyMDev/Nimble,phatblat/Nimble,jeffh/Nimble,Quick/Nimble,dgdosen/Nimble,dgdosen/Nimble,DanielAsher/Nimble,dgdosen/Nimble,Quick/Nimble,abbeycode/Nimble,DanielAsher/Nimble,twobitlabs/Nimble,phatblat/Nimble,phatblat/Nimble,AnthonyMDev/Nimble,twobitlabs/Nimble,jeffh/Nimble