Tweak installation instructions.

INSTALL

 # Installation instructions
 
-## Build the `galene` binary
+## Quick installation
+
+    CGO_ENABLED=0 go build -ldflags='-s -w'
+    mkdir groups
+    echo '{"presenter": [{}]}' > groups/test.json
+    ./galene &
+
+Then connect to `https://localhost:8443` and choose "test".
+
+## Full installation instructions
+
+### Build the `galene` binary
 
 You will need Go 1.16 or later (type `go version`).  Then do:
 
@@ -12,7 +23,7 @@ On Windows, do
     go build -ldflags="-s -w"
 
 
-## Set up a group
+### Set up a group
 
 Set up a group called *test* by creating a file `groups/test.json`:
 
@@ -29,7 +40,7 @@ You may use the following definition:
 See the README file for more details about defining groups.
 
 
-## Test locally
+### Test locally
 
     ./galene &
     
@@ -38,7 +49,7 @@ to the group that you have just set up in two distinct browser windows,
 then press *Ready* in one of the two; you should see a video in the other.
 
 
-## Configure your server's firewall
+### Configure your server's firewall
 
 If your server has a global IPv4 address and there is no firewall, there
 is nothing to do.
@@ -61,7 +72,7 @@ Galène's command line, where `203.0.113.1` is your NAT's external (global)
 IPv4 address.
 
 
-## Cross-compile for your server
+### Cross-compile for your server
 
 This step is only required if your server runs a different OS or has
 a different CPU than your build machine.
@@ -87,7 +98,7 @@ For a 32-bit MIPS board with no hardware floating point (WNDR3800, etc.):
     CGO_ENABLED=0 GOOS=linux GOARCH=mips GOMIPS=softfloat go build -ldflags='-s -w'
 
 
-## Deploy to your server
+### Deploy to your server
 
 Set up a user *galene* on your server, then do:
 
@@ -103,7 +114,8 @@ a certificate, install it in the files `data/cert.pem` and `data/key.pem`:
     sudo chown galene:galene data/*.pem
     sudo chmod go-rw data/key.pem
     
-Now run the binary on the server:
+Now arrange to run the binary on the server.  If you never reboot your
+server, it might be as simple as
 
     ssh galene@server.example.org
     ulimit -n 65536
@@ -135,7 +147,7 @@ If you are using *systemd*:
     WantedBy=multi-user.target
 
 
-# ICE Servers
+# Connectivity issues and ICE Servers
 
 Most connectivity issues are due to an incorrect ICE configuration.
 
@@ -197,8 +209,8 @@ look like this:
         }
     ]
 
-If you prefer to use coturn's `use-auth-secret` option, then the
-`ice-servers.json` file should look like this:
+It is more secure to use coturn's `use-auth-secret` option.  If you do
+that, then the `ice-servers.json` file should look like this:
 
     [
         {