Minor adjustments based on code review.

- reverse function true/false logic - now more logical from a function point of view, but completely incomprehensible on the receiving end of the function.
- darn yoda (Seriously, if you use strict checking - as I do -, why the heck would I need it ? makes code so much less readable...)

class-tgm-plugin-activation.php

@@ -573,7 +573,7 @@ protected function do_plugin_install() {
  // Only activate plugins if the config option is set to true.
  if ( $this->is_automatic ) {
  $plugin_activate = $upgrader->plugin_info(); // Grab the plugin info from the Plugin_Upgrader method.
- if( $this->activate_single_plugin( $plugin_activate, $slug, true ) === true ) {
+ if( false === $this->activate_single_plugin( $plugin_activate, $slug, true ) ) {
  return true; // Finish execution of the function early as we encountered an error
  }
 
@@ -603,7 +603,7 @@ protected function do_plugin_install() {
  elseif ( isset( $this->plugins[ $slug ]['file_path'], $_GET['tgmpa-activate'] ) && 'activate-plugin' === $_GET['tgmpa-activate'] ) {
  check_admin_referer( 'tgmpa-activate', 'tgmpa-activate-nonce' );
 
- if( $this->activate_single_plugin( $this->plugins[ $slug ]['file_path'], $slug ) === true ) {
+ if( false === $this->activate_single_plugin( $this->plugins[ $slug ]['file_path'], $slug ) ) {
  return true; // Finish execution of the function early as we encountered an error
  }
  }
@@ -689,7 +689,7 @@ public function maybe_adjust_source_dir( $source, $remote_source, $upgrader ) {
  * @param bool $automatic Whether this is an automatic activation after an install. Defaults to false.
  * This determines the styling of the output messages.
  *
- * @return bool True if an error was encountered, false otherwise.
+ * @return bool False if an error was encountered, true otherwise.
  */
  protected function activate_single_plugin( $file_path, $slug, $automatic = false ) {
 
@@ -699,7 +699,7 @@ protected function activate_single_plugin( $file_path, $slug, $automatic = false
  if ( is_wp_error( $activate ) ) {
  echo '<div id="message" class="error"><p>', wp_kses_post( $activate->get_error_message() ), '</p></div>',
  '<p><a href="', esc_url( $this->get_tgmpa_url() ), '" target="_parent">', esc_html( $this->strings['return'] ), '</a></p>';
- return true; // End it here if there is an error with activation.
+ return false; // End it here if there is an error with activation.
 
  } else {
  if ( ! $automatic ) {
@@ -724,7 +724,7 @@ protected function activate_single_plugin( $file_path, $slug, $automatic = false
  '</p></div>';
  }
 
- return false;
+ return true;
  }
 
  /**
@@ -751,7 +751,7 @@ public function notices() {
  return;
  }
 
- $installed_plugins = get_plugins(); // Retrieve a list of all the plugins
+ $installed_plugins  = get_plugins(); // Retrieve a list of all the plugins
  $message = array(); // Store the messages in an array to be outputted after plugins have looped through.
  $install_link = false; // Set to false, change to true in loop if conditions exist, used for action link 'install'.
  $install_link_count = 0; // Used to determine plurality of install action link text.