Fix Travis build

[mvz]

Summary

Fix Travis build by using default install task.

Details

Travis can't seem to find Bundler's exe file. Perhaps this is due to our custom install step?

Motivation and Context

All Travis builds are failing.

How Has This Been Tested?

By opening this pull request.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

[olleolleolle]

@mvz

AppVeyor summaries

Ruby 1.9, 2.0 in complains:

Gem::RuntimeRequirementNotMetError: ffi requires Ruby version < 2.5, >= 2.0. The

2.1, 2.2 complains (among other things)

Command "cmd.sh" not found in PATH-variable

and related errors which looked like the had the same reason.

[mvz]

@olleolleolle Those AppVeyor complaints should be fixed in #505. I guess we should merge in part of that to fix those basic errors.

[mvz]

Required builds on Travis are succesful; merging ...