Update Travis CI Ruby versions
Update Travis CI Ruby versions

Add

- MRI 2.4.0

Update

- MRI 2.2.5 to 2.2.6
- MRI 2.3.1 to 2.3.3
- JRuby 1.7.25 to 1.7.26
- JRuby 9.1.2.0 to 9.1.8.0

vmware/rbvmomi,10xEngineer/rbvmomi,10xEngineer/rbvmomi