title: How do i fix this error of 'simple_permissions' on flutter?
body: <p>There is an error when I run the code including simple_permissions on flutter project.</p>
  
  <pre><code>Initializing gradle...
  Resolving dependencies...
  Running Gradle task 'assembleDebug'...
  C:\Users\ria\Downloads\flutter_windows_v1.2.1-stable\flutter\.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:9: error: cannot find symbol
  import android.support.v4.app.ActivityCompat;
                               ^
    symbol:   class ActivityCompat
    location: package android.support.v4.app
  C:\Users\ria\Downloads\flutter_windows_v1.2.1-stable\flutter\.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:10: error: package android.support.v4.content does not exist
  import android.support.v4.content.ContextCompat;
                                   ^
  C:\Users\ria\Downloads\flutter_windows_v1.2.1-stable\flutter\.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:156: error: cannot find symbol
          ActivityCompat.requestPermissions(activity, perm, 0);
          ^
    symbol:   variable ActivityCompat
    location: class SimplePermissionsPlugin
  C:\Users\ria\Downloads\flutter_windows_v1.2.1-stable\flutter\.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:163: error: cannot find symbol
          return PackageManager.PERMISSION_GRANTED == ContextCompat.checkSelfPermission(activity, permission);
                                                      ^
    symbol:   variable ContextCompat
    location: class SimplePermissionsPlugin
  C:\Users\ria\Downloads\flutter_windows_v1.2.1-stable\flutter\.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:171: error: cannot find symbol
              if (ActivityCompat.shouldShowRequestPermissionRationale(registrar.activity(), permission)) {
                  ^
    symbol:   variable ActivityCompat
    location: class SimplePermissionsPlugin
  C:\Users\ria\Downloads\flutter_windows_v1.2.1-stable\flutter\.pub-cache\hosted\pub.dartlang.org\simple_permissions-0.1.9\android\src\main\java\com\ethras\simplepermissions\SimplePermissionsPlugin.java:175: error: cannot find symbol
                  if (ActivityCompat.checkSelfPermission(registrar.context(), permission) == PackageManager.PERMISSION_GRANTED) {
                      ^
    symbol:   variable ActivityCompat
    location: class SimplePermissionsPlugin
  6 errors
  
  FAILURE: Build failed with an exception.
  
  * What went wrong:
  Execution failed for task ':simple_permissions:compileDebugJavaWithJavac'.
  &gt; Compilation failed; see the compiler error output for details.
  
  * Try:
  Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.
  
  * Get more help at https://help.gradle.org
  
  BUILD FAILED in 2s
  Finished with error: Gradle task assembleDebug failed with exit code 1
  *******************************************************************************************
  The Gradle failure may have been because of AndroidX incompatibilities in this Flutter app.
  
  *******************************************************************************************
  </code></pre>