Using 'a big triangle' rather than '2 triangles'

see https://github.com/ProjectSeptemberInc/gl-react/issues/60

android/src/main/java/com/projectseptember/RNGL/GLCanvas.java

@@ -723,7 +723,7 @@ public class GLCanvas extends GLSurfaceView
 
         glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
         glClear(GL_COLOR_BUFFER_BIT);
-        glDrawArrays(GL_TRIANGLES, 0, 6);
+        glDrawArrays(GL_TRIANGLES, 0, 3);
     }
 
     private void render () {

android/src/main/java/com/projectseptember/RNGL/GLShader.java

@@ -190,11 +190,8 @@ public class GLShader {
 
         float buf[] = {
             -1.0f, -1.0f,
-                1.0f, -1.0f,
-                -1.0f,  1.0f,
-                -1.0f,  1.0f,
-                1.0f, -1.0f,
-                1.0f,  1.0f
+            -1.0f, 4.0f,
+             4.0f,  -1.0f
         };
         FloatBuffer bufferData = ByteBuffer.allocateDirect(buf.length * 4)
                 .order(ByteOrder.nativeOrder())

ios/GLCanvas.m

@@ -520,7 +520,7 @@ RCT_NOT_IMPLEMENTED(-init)
       RCT_PROFILE_BEGIN_EVENT(0, @"draw", nil);
       glClearColor(0.0, 0.0, 0.0, 0.0);
       glClear(GL_COLOR_BUFFER_BIT);
-      glDrawArrays(GL_TRIANGLES, 0, 6);
+      glDrawArrays(GL_TRIANGLES, 0, 3);
       RCT_PROFILE_END_EVENT(0, @"gl", nil);
 
       RCT_PROFILE_END_EVENT(0, @"gl", nil);

ios/GLShader.m

@@ -389,11 +389,8 @@ GLuint compileShader (NSString* shaderName, NSString* shaderString, GLenum shade
   glBindBuffer(GL_ARRAY_BUFFER, buffer);
   GLfloat buf[] = {
     -1.0, -1.0,
-    1.0, -1.0,
-    -1.0,  1.0,
-    -1.0,  1.0,
-    1.0, -1.0,
-    1.0,  1.0
+    -1.0, 4.0,
+     4.0,  -1.0
   };
   glBufferData(GL_ARRAY_BUFFER, sizeof(buf), buf, GL_STATIC_DRAW);