Updates travis matrix to new ruby versions.

[LeFnord]

No description provided.

[grape-bot]

	1 Warning
⚠️	Unless you’re refactoring existing code, please update CHANGELOG.md.

Here's an example of a CHANGELOG.md entry:

* [#783](https://github.com/ruby-grape/grape-swagger/pull/783): Updates travis matrix to new ruby versions - [@LeFnord](https://github.com/LeFnord).

Generated by 🚫 danger

[coveralls]

Coverage increased (+0.002%) to 99.455% when pulling 0a2257d on LeFnord:master into 05939a0 on ruby-grape:master.

[coveralls]

Coverage increased (+0.002%) to 99.455% when pulling 0a2257d on LeFnord:master into 05939a0 on ruby-grape:master.

[coveralls]

Coverage increased (+0.002%) to 99.455% when pulling 0a2257d on LeFnord:master into 05939a0 on ruby-grape:master.

[coveralls]

Coverage increased (+0.002%) to 99.455% when pulling 0a2257d on LeFnord:master into 05939a0 on ruby-grape:master.

[coveralls]

Coverage increased (+0.002%) to 99.454% when pulling 0a2257d on LeFnord:master into 05939a0 on ruby-grape:master.