Update README.md to reflect current beta status of repo

Author: neil.hamilton

README.md

@@ -31,6 +31,8 @@ The driver will work with the following PicoScope models:
 * [Instrument Control Toolbox](http://www.mathworks.co.uk/products/instrument/)
 * The [PicoScope Support Toolbox](http://uk.mathworks.com/matlabcentral/fileexchange/53681-picoscope-support-toolbox)
 
+**Currently with this beta release only 64-bit MATLAB on Windows is supported.  Support for other operation systems will come in further updates.**
+
 **Note:** MATLAB 2015b is recommended for 32-bit versions of MATLAB on Microsoft Windows operating systems.
 
 ### Installing the Instrument Driver files
@@ -58,10 +60,6 @@ Please visit our [Support page](https://www.picotech.com/tech-support) to contac
 
 Please leave a comment and rating for this submission on our [MATLAB Central File Exchange page]().
 
-## Contributing
-
-Contributions to examples are welcome. Refer to our [guidelines for contributing](.github/CONTRIBUTING.md) for further information.
-
 ## Versioning
 
 For the versions available, and release notes, refer to the [Releases](https://github.com/picotech/picosdk-ps6000a-matlab-instrument-driver/releases) page.