travis: stop testing tip
travis: stop testing tip

tip seems to always fail at the moment due to a problem with
the unit testing framework. Disabling tip for now until the problem
is resolved.

https://github.com/smartystreets/goconvey/issues/476

EtienneBruines/golearn,thedadams/golearn,sjwhitworth/golearn,thedadams/golearn,sjwhitworth/golearn,EtienneBruines/golearn,thedadams/golearn,sjwhitworth/golearn,sjwhitworth/golearn,sjwhitworth/golearn,EtienneBruines/golearn,thedadams/golearn