First pass at documentation updates for the Memory Adapter

docs/memory.md

@@ -12,6 +12,13 @@ Under the hood, the memory adapter stores data in a dictionary like so:
       User1: true,
       User2: false
     }
+  },
+  some_flag_name_with_treatments: {
+    treatment_contexts: {
+      User1: 'treatment_name_1',
+      User2: 'treatment_name_2',
+      User3: 'treatment_name_3'
+    }
   }
 }
 ```
@@ -79,6 +86,47 @@ ThisFeature.test_adapter.on!(:flag_name, context: user) # with context
 ThisFeature.test_adapter.off!(:flag_name)               # without context
 ```
 
+### **#enable_treatment!**
+
+This method is useful when you need to enable a feature flag with a treatment (or multiple treatments), and not just `"on"` and `"off"`.
+
+Usage example of these:
+
+```ruby
+# If you have configured the in-memory adapter as the default
+ThisFeature.test_adapter.enable_treatment!(:flag_name, treatment: 'treatment_name', context: user)
+```
+#### This method requires 3 arguments:
+1. `flag_name`: String or Symbol (not a named argument)
+2. `treatment`: String
+3. `context`: User or Org object
+
+Per flag name, there can only be one treatment per `context_key` (the ID of object that is provided as `context`). So multiple calls with the same `context`, but different treatment names, will be overwritten.
+
+```ruby
+ThisFeature.test_adapter.enable_treatment!('flag_a', treatment: 'treatment_1', context: user1)
+ThisFeature.test_adapter.storage # => { 'flag_a' => { :treatment_contexts => { 'User1': 'treatment_1' } } }
+
+ThisFeature.test_adapter.enable_treatment!(:flag_a, treatment: 'treatment_2', context: user1)
+ThisFeature.test_adapter.storage # => { 'flag_a' => { :treatment_contexts => { 'User1': 'treatment_2' } } }
+```
+
+### **#treatment_value**
+
+You can retrieve the flag's treatment name for a specific context.
+
+Usage example of these:
+
+```ruby
+# If you have configured the in-memory adapter as the default
+ThisFeature.test_adapter.treatment_value(:flag_name, context: user)
+```
+
+#### This method requires 2 arguments:
+1. `flag_name`: String or Symbol (not a named argument)
+2. `context`: User or Org object
+
+When the Memory storage does not contain the given flag_name or if there is no provided `context`, `"control"` is returned. This is meant to mimic what SplitIO would return in the case of no configured treatment for the given `context`.
 ### **#clear**
 
 Since the memory adapter stores flags in memory, it won't automatically get cleaned up in your tests. You can use this method to reset the memory adapter state.