Adjusted CI testing scripts

ci/rustup.sh

@@ -7,6 +7,5 @@ set -ex
 export TRAVIS_RUST_VERSION
 for TRAVIS_RUST_VERSION in 1.8.0 stable beta nightly; do
     run="rustup run $TRAVIS_RUST_VERSION"
-    $run cargo build --verbose
     $run $PWD/ci/test_full.sh
 done

ci/test_full.sh

@@ -13,5 +13,7 @@ cargo build --verbose --no-default-features
 cargo test --verbose --no-default-features
 
 # test `i128`
-cargo build --verbose --features=i128
-cargo test --verbose --features=i128
+if [[ "$TRAVIS_RUST_VERSION" =~ ^(nightly|beta)$ ]]; then
+    cargo build --verbose --features=i128
+    cargo test --verbose --features=i128
+fi