Implement basic metrics layout & total elapsed time (#1250)

* Initial metadata processing

* Dynamic coloring and other stuff

* Use -vv / --meta

* More testing

* Cleanup

* Tweek message

Co-authored-by: Jakub Roztocil <jakub@roztocil.co>

docs/README.md

@@ -1497,13 +1497,15 @@ By default, HTTPie only outputs the final response and the whole response
 Content-Length: 477
 Content-Type: application/json
 Date: Sun, 05 Aug 2012 00:25:23 GMT
-    […]
-}
-```
-
-### Quiet output
-
-`--quiet` redirects all output that would otherwise go to `stdout` and `stderr` to `/dev/null` (except for errors and warnings).
+Server: gunicorn/0.13.4
+
+{
+    […]
+}
+```
+
+#### Verbosity Level: 2
+
 If you run HTTPie with `-vv` or `--verbose --verbose`, then it would also display the response metadata.
 
 ```bash
@@ -1516,6 +1518,7 @@ It accepts a string of characters each of which represents a specific part of th
 `--quiet` redirects all output that would otherwise go to `stdout` and `stderr` to `/dev/null` (except for errors and warnings).
 This doesn’t affect output to a file via `--output` or `--download`.
 
+```bash
 # There will be no output:
 $ http --quiet pie.dev/post enjoy='the silence'
 ```
@@ -1552,6 +1555,15 @@ Server: gunicorn/0.13.4
 As an optimization, the response body is downloaded from the server only if it’s part of the output.
 This is similar to performing a `HEAD` request, except that it applies to any HTTP method you use.
 
+Let’s say that there is an API that returns the whole resource when it is updated, but you are only interested in the response headers to see the status code after an update:
+
+```bash
+$ http --headers PATCH pie.dev/patch name='New Name'
+```
+
+Since you are only printing the HTTP headers here, the connection to the server is closed as soon as all the response headers have been received.
+Therefore, bandwidth and time isn’t wasted downloading the body which you don’t care about.
+The response headers are downloaded always, even if they are not part of the output
 
 ## Raw request body