Use Rust 1.48.0 for rustfmt, clippy, and tarpaulin jobs.

Additionally, combine `rustfmt` and `clippy` jobs for build performance
reasons. #223

.travis.yml

@@ -18,20 +18,16 @@ jobs:
       cargo test --verbose --no-default-features --features "autoconvert f32 si use_serde try-from"
       cargo test --verbose --no-run --no-default-features --features "autoconvert usize isize bigint bigrational si std use_serde try-from"
       cargo test --verbose --no-run --no-default-features --features "autoconvert usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 bigint biguint rational rational32 rational64 bigrational f32 f64 std use_serde try-from"
-  - name: Rustfmt
-    rust: 1.47.0
+  - name: Clippy & Rustfmt
+    rust: 1.48.0
     install:
-    - rustup component add rustfmt
-    script: |
-      cargo fmt -- --check
-  - name: Clippy
-    rust: 1.47.0
-    install:
-    - rustup component add clippy
+    - rustup component add clippy rustfmt
     script: |
+      set -e
       RUSTFLAGS="-D warnings" cargo clippy --all --tests
+      cargo fmt -- --check
   - name: Tarpaulin
-    rust: 1.47.0
+    rust: 1.48.0
     script: |
       docker run --security-opt seccomp=unconfined -v "$PWD:/volume" xd009642/tarpaulin sh -c "cargo build && cargo tarpaulin --ciserver travis-ci --coveralls $TRAVIS_JOB_ID"
   - rust: stable