Build with lowest supported rustc version on Travis.

Author: bodil

.travis.yml

@@ -1,23 +1,24 @@
 language: rust
 rust:
-    - stable
-    - beta
-    - nightly
+  - 1.46.0
+  - stable
+  - beta
+  - nightly
 arch:
-    - amd64
-    - arm64
-    - ppc64le
-    - s390x
+  - amd64
+  - arm64
+  - ppc64le
+  - s390x
 
 cache:
-    directories:
-        - /home/travis/.rustup
-        - /home/travis/.cargo
-        - /home/travis/target
+  directories:
+    - /home/travis/.rustup
+    - /home/travis/.cargo
+    - /home/travis/target
 
 install:
-    - rustup update
-    - mkdir -p .cargo && echo '[build]' > .cargo/config && echo 'target-dir = "/home/travis/target"'
-      >> .cargo/config
+  - rustup update
+  - mkdir -p .cargo && echo '[build]' > .cargo/config && echo 'target-dir = "/home/travis/target"'
+    >> .cargo/config
 
 script: cargo test