Upgrade handlebars to 4.1.0.

The whitespace changes in tests are because of this bugfix:
<sunng87/handlebars-rust#448>.

Author: mkantor

Cargo.lock

@@ -35,7 +35,7 @@ actix-web = "3.3.2"
 anyhow = "1.0.41"
 bytes = "0.5.6"
 futures = "0.3.15"
-handlebars = "4.0.0"
+handlebars = "4.1.0"
 log = "0.4.14"
 mime = "0.3.16"
 mime_guess = "2.0.3"

Cargo.toml

@@ -505,7 +505,7 @@ mod tests {
 
         let template = "this is partial: {{> abc.html.hbs}}";
         let expected_output =
-            "this is partial: a\nb\n\nc\n\nsubdirectory entries:\n/subdirectory/c";
+            "this is partial: a\nb\nc\n\nsubdirectory entries:\n/subdirectory/c\n";
 
         let renderable = content_engine
             .new_template(
@@ -536,7 +536,7 @@ mod tests {
         let content_engine = shared_content_engine.read().unwrap();
 
         let route = route("/abc");
-        let expected_output = "a\nb\n\nc\n\nsubdirectory entries:\n/subdirectory/c";
+        let expected_output = "a\nb\nc\n\nsubdirectory entries:\n/subdirectory/c\n";
 
         let content = content_engine
             .get(&route)

src/content/content_engine.rs

@@ -5,9 +5,9 @@ input_file: samples/partials
 
 ---
 a.html.hbs: "a\n"
-ab.html.hbs: "a\nb\n\n"
-abc.html.hbs: "a\nb\n\nc\n\nsubdirectory entries:\n/subdirectory/c"
+ab.html.hbs: "a\nb\n"
+abc.html.hbs: "a\nb\nc\n\nsubdirectory entries:\n/subdirectory/c\n"
 b.html: "b\n"
-subdirectory.html.hbs: "subdirectory entries:\n/subdirectory/c"
+subdirectory.html.hbs: "subdirectory entries:\n/subdirectory/c\n"
 subdirectory/c.html.hbs: "c\n"