readme: Updated Readme (#173)

Author: msohailhussain

README.md

@@ -67,9 +67,77 @@ The Optimizely client object accepts the following plug-ins:
 1. `IEventDispatcher` handles the HTTP requests to Optimizely.  The default implementation is an asynchronous "fire and forget".
 2. `ILogger` exposes a single method, Log, to record activity in the SDK.  An example of a class to bridge the SDK's Log to Log4Net is provided in the Demo Application.
 3. `IErrorHandler` allows you to implement custom logic when Exceptions are thrown.  Note that Exception information is already included in the Log.
+4. `ProjectConfigManager` exposes method for retrieving ProjectConfig instance. Examples include `FallbackProjectConfigManager` and `HttpProjectConfigManager`.
 
 These are optional plug-ins and default behavior is implement if none are provided.
 
+#### OptimizelyFactory
+
+[`OptimizelyFactory`](https://github.com/optimizely/csharp-sdk/blob/master/OptimizelySDK/OptimizelyFactory.cs)
+provides basic utility to instantiate the Optimizely SDK with a minimal number of configuration options.
+
+`OptimizelyFactory` does not capture all configuration and initialization options. For more use cases,
+build the resources via their respective builder classes.
+
+##### Use OptimizelyFactory
+
+You must provide the SDK key at runtime, either directly via the factory method:
+```
+Optimizely optimizely = OptimizelyFactory.newDefaultInstance(<<SDK_KEY>>);
+```
+
+You can also provide default datafile with the SDK key.
+```
+Optimizely optimizely = OptimizelyFactory.newDefaultInstance(<<SDK_KEY>>, <<Fallback>>);
+```
+
+#### HttpProjectConfigManager
+
+[`HttpProjectConfigManager`](https://github.com/optimizely/csharp-sdk/blob/master/OptimizelySDK/Config/HttpProjectConfigManager.cs)
+is an implementation of the abstract [`PollingProjectConfigManager`](https://github.com/optimizely/csharp-sdk/blob/master/OptimizelySDK/Config/PollingProjectConfigManager.cs).
+The `Poll` method is extended and makes an HTTP GET request to the configured URL to asynchronously download the
+project datafile and initialize an instance of the ProjectConfig.
+
+By default, `HttpProjectConfigManager` will block until the first successful datafile retrieval, up to a configurable timeout.
+Set the frequency of the polling method and the blocking timeout with `HttpProjectConfigManager.Builder`.
+
+##### Use HttpProjectConfigManager
+
+```
+HttpProjectConfigManager httpManager = new HttpProjectConfigManager.Builder()
+	.WithSdkKey(sdkKey)
+	.WithPollingInterval(TimeSpan.FromMinutes(1))
+	.Build();
+```
+
+##### SDK key
+
+The SDK key is used to compose the outbound HTTP request to the default datafile location on the Optimizely CDN.
+
+##### Polling interval
+
+The polling interval is used to specify a fixed delay between consecutive HTTP requests for the datafile. Between 1 to 4294967294 miliseconds is valid duration. Otherwise default 5 minutes will be used.
+
+##### Blocking Timeout Period
+
+The blocking timeout period is used to specify a maximum time to wait for initial bootstrapping. Between 1 to 4294967294 miliseconds is valid blocking timeout period. Otherwise default value 15 seconds will be used.
+
+##### Initial datafile
+
+You can provide an initial datafile via the builder to bootstrap the `ProjectConfigManager` so that it can be used immediately without blocking execution.
+
+##### URL
+
+The URL is used to specify the location of datafile.
+
+##### Format
+
+This option enables user to provide a custom URL format to fetch the datafile.
+
+##### Start by default
+
+This option is used to specify whether to start the config manager on initialization.
+
 ## Development
 
 ### Unit tests