Fix flag syntax (#16)

* Fix "--enable-dotnet-core-binding" flag in documentation

README.md

@@ -19,7 +19,7 @@ git clone --recursive https://github.com/Azure/azure-iot-gateway-sdk.git
 git checkout 09bbcb7feaf5acc3913abd722b96e993238edd0c
 ```
 
-The gateway needs to be build with the ```--enable_dotnetcore_binding``` flag to enable it to run this module.
+The gateway needs to be build with the ```--enable-dotnet-core-binding``` flag to enable it to run this module.
 # Directory Structure
 
 ## /samples
@@ -90,7 +90,7 @@ The JSON snippet above shows the default security settings, which can thus be om
 
 To run the module and have it publish to IoT Hub, configure the name of your Hub (JSON field ```"IoTHubName"```) and the IoT Hub device ID and shared access key to use (JSON fields ```"Id"``` and ```"SharedAccessKey"```) in your version of ```gateway_config.json```.  Note that if you use a "Mapping" module in your configuration, you can omit the ```"SharedAccessKey"``` field.  Finally, ensure that the right native module is configured, based on your platform (i.e. iothub.dll for Windows, libiothub.so for Linux, etc.).
 
-You can build a sample gateway host as part of the Azure IoT Gateway SDK build system.  Ensure that you pass the ```--enable_dotnetcore_binding``` to the build script and use one of the resulting sample gateway hosts.   
+You can build a sample gateway host as part of the Azure IoT Gateway SDK build system.  Ensure that you pass the ```--enable-dotnet-core-binding``` to the build script and use one of the resulting sample gateway hosts.   
 
 To simplify this step, and to build a sample gateway to host the OPC-UA module - along with the module itself - clone the gateway SDK repo to your device and run the build script with the ```-i <root-of-sdk>```.  The resulting release folder will contain not just the module and managed dependencies, but also a native IoT Hub proxy module as well as a ```sample_gateway``` executable that you can pass the updated JSON configuration to.