fix panic from Gzip reading an empty stream

Closes #82

tests/client.rs

@@ -344,3 +344,62 @@ fn test_gzip_response() {
 
     assert_eq!(body, "test request");
 }
+
+#[test]
+fn test_gzip_empty_body() {
+    let server = server! {
+        request: b"\
+            HEAD /gzip HTTP/1.1\r\n\
+            Host: $HOST\r\n\
+            User-Agent: $USERAGENT\r\n\
+            Accept: */*\r\n\
+            Accept-Encoding: gzip\r\n\
+            \r\n\
+            ",
+        response: b"\
+            HTTP/1.1 200 OK\r\n\
+            Server: test-accept\r\n\
+            Content-Encoding: gzip\r\n\
+            Content-Length: 100\r\n\
+            \r\n"
+    };
+
+    let client = reqwest::Client::new().unwrap();
+    let mut res = client.head(&format!("http://{}/gzip", server.addr()))
+        .send()
+        .unwrap();
+
+    let mut body = ::std::string::String::new();
+    res.read_to_string(&mut body).unwrap();
+
+    assert_eq!(body, "");
+}
+
+#[test]
+fn test_gzip_invalid_body() {
+    let server = server! {
+        request: b"\
+            GET /gzip HTTP/1.1\r\n\
+            Host: $HOST\r\n\
+            User-Agent: $USERAGENT\r\n\
+            Accept: */*\r\n\
+            Accept-Encoding: gzip\r\n\
+            \r\n\
+            ",
+        response: b"\
+            HTTP/1.1 200 OK\r\n\
+            Server: test-accept\r\n\
+            Content-Encoding: gzip\r\n\
+            Content-Length: 100\r\n\
+            \r\n\
+            0"
+    };
+
+    let mut res = reqwest::get(&format!("http://{}/gzip", server.addr()))
+        .unwrap();
+    // this tests that the request.send() didn't error, but that the error
+    // is in reading the body
+
+    let mut body = ::std::string::String::new();
+    res.read_to_string(&mut body).unwrap_err();
+}