travis: enable bionic & multi-cpu testing

Author: xnox

.travis.yml

@@ -1,5 +1,6 @@
 language: python
 python: 3.7
+dist: bionic
 
 # To turn off cached cython files and compiler cache
 # set NOCACHE-true
@@ -23,6 +24,12 @@ git:
   # for cloning
   depth: false
 
+arch:
+  - amd64
+  - ppc64le
+  - s390x
+  - arm64
+
 matrix:
   fast_finish: true