Revert "fix hidden check to use also alpha value"

This reverts commit e29b3b3a579c29db630dbf39bc535c780982927c.
Bump to 3.1.1
Allow Travis to use container based builds
Let `continueAfterFailure` default to YES

Setting the `continueAfterFailure` property to `NO` is very problematic when using the XCTest asynchronous API or the `KIFTestActor runBlock:` API since it may cause uncatchable exceptions.