Re-enable minimal dependency version testing on nightly runners

Author: dhardy

.travis.yml

@@ -37,6 +37,9 @@ matrix:
         - rm -rf target/doc
         - cargo doc --no-deps --all --all-features
         - cargo deadlinks --dir target/doc
+        # also test minimum dependency versions are usable
+        - cargo generate-lockfile -Z minimal-versions
+        - cargo test
 
     - rust: nightly
       os: osx
@@ -52,6 +55,9 @@ matrix:
         - rm -rf target/doc
         - cargo doc --no-deps --all --all-features
         - cargo deadlinks --dir target/doc
+        # also test minimum dependency versions are usable
+        - cargo generate-lockfile -Z minimal-versions
+        - cargo test
 
     - rust: nightly
       env: DESCRIPTION="WASM via emscripten, stdweb and wasm-bindgen"
@@ -97,6 +103,14 @@ matrix:
         #- cargo build --target=x86_64-unknown-fuchsia --all-features
         - cargo build --target=x86_64-unknown-netbsd --all-features
         - cargo build --target=x86_64-unknown-redox --all-features
+        # also test minimum dependency versions are usable
+        - cargo generate-lockfile -Z minimal-versions
+        - cargo build --target=x86_64-sun-solaris --all-features
+        - cargo build --target=x86_64-unknown-cloudabi --all-features
+        - cargo build --target=x86_64-unknown-freebsd --all-features
+        #- cargo build --target=x86_64-unknown-fuchsia --all-features
+        - cargo build --target=x86_64-unknown-netbsd --all-features
+        - cargo build --target=x86_64-unknown-redox --all-features
 
     # Trust cross-built/emulated targets. We must repeat all non-default values.
     - rust: stable