Allow downloading of large tests from EF github and fix issues with serde

eth2/state_processing/yaml_utils/build.rs

@@ -0,0 +1,28 @@
+extern crate reqwest;
+extern crate tempdir;
+
+use std::fs::File;
+use std::io::copy;
+
+fn main() {
+    // These test files are not to be stored in the lighthouse repo as they are quite large (32MB).
+    // They will be downloaded at build time by yaml-utils crate (in build.rs)
+    let git_path = "https://raw.githubusercontent.com/ethereum/eth2.0-tests/master/state/";
+    let test_names = vec![
+        "sanity-check_default-config_100-vals.yaml",
+        "sanity-check_small-config_32-vals.yaml",
+    ];
+
+    for test in test_names {
+        let mut target = String::from(git_path);
+        target.push_str(test);
+        let mut response = reqwest::get(target.as_str()).unwrap();
+
+        let mut dest = {
+            let mut file_name = String::from("specs/");
+            file_name.push_str(test);
+            File::create(file_name).unwrap()
+        };
+        copy(&mut response, &mut dest).unwrap();
+    }
+}