Add paragraphs in README on how to configure cluster and replication.

[ci skip]

README.md

@@ -117,7 +117,7 @@ are usually lazily initialized only when needed. Predis by default supports the
   - `prefix`: a prefix string that is automatically applied to keys found in commands.
   - `exceptions`: whether the client should throw or return responses upon Redis errors.
   - `connections`: connection backends or a connection factory to be used by the client.
-  - `cluster`: which backend to use for clustering (predis, redis or custom configuration).
+  - `cluster`: which backend to use for clustering (`predis`, `redis` or custom configuration).
   - `replication`: which backend to use for replication (predis or custom configuration).
   - `aggregate`: custom connections aggregator (overrides both `cluster` and `replication`).
 
@@ -133,6 +133,65 @@ backed solution using [redis-cluster](http://redis.io/topics/cluster-tutorial).
 Predis can handle single-master and multiple-slaves setups by executing read operations on slaves
 and switching to the master for write operations. The replication behaviour is fully configurable.
 
+## Replication ##
+
+The client can be configured to work in a master / slave replication setup by executing read-only
+commands on slave nodes and automatically switch to the master node as soon as a command performing
+a write operation is executed. This is the basic configuration needed work with replication:
+
+```php
+$parameters = ['tcp://10.0.0.1?alias=master', 'tcp://10.0.0.2?alias=slave-01'];
+$options    = ['replication' => true];
+
+$client = new Predis\Client($parameters, $options);
+```
+
+While Predis is able to distinguish commands performing write and read-only operations, `EVAL` and
+`EVALSHA` represent a corner case in which the client switches to the master node because it is not
+able to tell when a Lua script is safe to be executed on slaves. While this is the default behavior,
+when certain Lua scripts do not perform write operations it is possible to provide an hint to tell
+the client to stick with slaves for their execution.
+
+```php
+$parameters = ['tcp://10.0.0.1?alias=master', 'tcp://10.0.0.2?alias=slave-01'];
+$options    = ['replication' => function () {
+    $strategy = new Predis\Replication\ReplicationStrategy();
+
+    // This exact script won't trigger a switch from slave to the master node.
+    $strategy->setScriptReadOnly($READONLY_LUA_SCRIPT);
+
+    return new Predis\Connection\Aggregate\MasterSlaveReplication($strategy);
+}];
+
+$client = new Predis\Client($parameters, $options);
+$client->eval($READONLY_LUA_SCRIPT, 0);             // Sticks to slave using `eval`...
+$client->evalsha(sha1($READONLY_LUA_SCRIPT), 0);    // ... and `evalsha`, too.
+```
+
+The `examples` directory contains two complete scripts showing how replication can be configured in
+a [simple](examples/replication_simple.php) and a [more complex](examples/replication_complex.php)
+scenario.
+
+## Clustering ##
+
+Simply passing an array of connection parameters to the client constructor configures Predis to work
+in clustering mode using client-side sharding. If you, on the other hand, want to leverage Redis >=
+3.0 nodes coordinated by redis-cluster, then the client must be initialized like this:
+
+```php
+$parameters = ['tcp://10.0.0.1', 'tcp://10.0.0.2'];
+$options    = ['cluster' => redis];
+
+$client = new Predis\Client($parameters, $options);
+```
+
+When using redis-cluster, it is not necessary to pass all of the nodes forming your cluster but you
+can simply specify only a few nodes and Predis will automatically fetch the full and updated slots
+map directly from Redis by contacting one of the nodes.
+
+NOTE: our support for redis-cluster does not currently consider master/slave replication but this
+feature will be added in a future release of this library.
+
 
 ### Command pipelines ###