Update README.md

Changed link to point to beta testing page

README.md

@@ -11,7 +11,7 @@ the use of
 [material principles](https://www.google.com/design/spec/material-design/introduction.html#introduction-principles)
 to create tactile, bold, understandable UIs.
 
-**[Install on Google Play](https://play.google.com/store/apps/details?id=io.plaidapp)**
+**[Install on Google Play (Beta Testing)](https://play.google.com/apps/testing/io.plaidapp)**
 
 
 ### Screenshots
@@ -43,4 +43,4 @@ distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 License for the specific language governing permissions and limitations under
 the License.
-```
+```