improve documentation (#7)

README.md

@@ -9,7 +9,7 @@ pytest plugin for lockable resources.
 Replacement for Jenkins lockable -plugin.
 Locking is implemented using `<resource.id>.lock` files.
 
-Resources are described in json file as array of objects. Each object has some mandatory fields but can contains any other as well. Required fields are: `id`, `online`, `hostname`-
+Resources are described in json file as array of objects. Each object has some mandatory fields but can contains any other as well. Required fields are: `id`, `online`, `hostname`.
 
 ## Example `resources.json`
 
@@ -18,13 +18,20 @@ Resources are described in json file as array of objects. Each object has some m
   {
     "id": "1234",
     "online": true,
-    "hostname": "localhost"
+    "hostname": "localhost",
+    "os": "Android"
   }
 ]
 ```
 
 `id` should be unique for each resources. `online` describes if resource are available for allocator. Set this `false`  if you don't want to allocate resource. `hostname` is used to select suitable resource by running host. 
 
+Usage:
+```
+pytest --allocation_hostname localhost -s --allocation_requirements os=Android my_test
+```
+
+
 ## installation
 
 **Requires:** python 3.7<
@@ -59,5 +66,5 @@ Example:
 See [example test](example/test_example.py). Usage:
 ```
 cd example
-pytest --allocation_hostname localhost -s --allocation_lock_folder .  .
+pytest --allocation_hostname localhost -s --allocation_lock_folder . .
 ```