Remove Travis CI configuration (#484)

The migration to GitHub Actions occurred quite awhile ago and Travis CI
is no longer used

.travis.yml

@@ -1,41 +0,0 @@
-language: rust
-
-rust:
-  - stable
-  - nightly
-
-env:
-  # Tests the u32 backend
-  - TEST_COMMAND=test EXTRA_FLAGS='--no-default-features' FEATURES='std u32_backend'
-  # Tests the u64 backend
-  - TEST_COMMAND=test EXTRA_FLAGS='--no-default-features' FEATURES='std u64_backend'
-  # Tests the fiat_u32 backend
-  - TEST_COMMAND=test EXTRA_FLAGS='--no-default-features' FEATURES='std fiat_u32_backend'
-  # Tests the fiat_u64 backend
-  - TEST_COMMAND=test EXTRA_FLAGS='--no-default-features' FEATURES='std fiat_u64_backend'
-  # Tests the simd backend
-  - TEST_COMMAND=test EXTRA_FLAGS='--no-default-features' FEATURES='std simd_backend'
-  # Tests serde support and default feature selection
-  - TEST_COMMAND=test EXTRA_FLAGS='' FEATURES='serde'
-  # Tests building without std. We have to select a backend, so we select the one
-  # most likely to be useful in an embedded environment.
-  - TEST_COMMAND=build EXTRA_FLAGS='--no-default-features' FEATURES='u32_backend'
-  # Tests no_std+alloc usage using the most embedded-friendly backend
-  - TEST_COMMAND=test EXTRA_FLAGS='--lib --no-default-features' FEATURES='alloc u32_backend'
-
-matrix:
-  exclude:
-    # Test the simd backend only on nightly
-    - rust: stable
-      env: TEST_COMMAND=test EXTRA_FLAGS='--no-default-features' FEATURES='std simd_backend'
-    # Test no_std+alloc only on nightly
-    - rust: stable
-      env: TEST_COMMAND=test EXTRA_FLAGS='--lib --no-default-features' FEATURES='alloc u32_backend'
-
-script:
-  - cargo $TEST_COMMAND --features="$FEATURES" $EXTRA_FLAGS
-
-notifications:
-  slack:
-    rooms:
-      - dalek-cryptography:Xxv9WotKYWdSoKlgKNqXiHoD#dalek-bots

Cargo.toml

@@ -21,7 +21,6 @@ description = "A pure-Rust implementation of group operations on ristretto255 an
 exclude = [
     "**/.gitignore",
     ".gitignore",
-    ".travis.yml",
 ]
 
 [package.metadata.docs.rs]
@@ -32,9 +31,6 @@ rustdoc-args = [
 rustc-args = ["--cfg", "curve25519_dalek_backend=\"simd\""]
 features = ["serde", "rand_core", "digest"]
 
-[badges]
-travis-ci = { repository = "dalek-cryptography/curve25519-dalek", branch = "master"}
-
 [dev-dependencies]
 sha2 = { version = "0.10", default-features = false }
 bincode = "1"