Fetching README.md when not needed

[bradmkjr]

The get_new_version function loads up the base file and then also loads up README.md without checking if a valid version number was found in base file.

I recommend replacing get_new_version with the following:

    /**
     * Get New Version from github
     *
     * @since 1.0
     * @return int $version the version number
     */
    public function get_new_version() {
        $version = get_site_transient( $this->config['slug'].'_new_version' );

        if ( $this->overrule_transients() || ( !isset( $version ) || !$version || '' == $version ) ) {

            $raw_response = $this->remote_api_get( trailingslashit( $this->config['api_url'] ). basename( $this->config['slug'] ) );

            if ( is_wp_error( $raw_response ) )
                $version = false;

            if (is_array($raw_response)) {
                if (!empty($raw_response['body']))
                    preg_match( '#^\s*Version\:\s*(.*)$#im', $raw_response['body'], $matches );
            }

            if ( empty( $matches[1] ) )
                $version = false;
            else
                $version = $matches[1];

            if( ! $version ){
                // back compat for older readme version handling
                $raw_response = $this->remote_api_get( trailingslashit( $this->config['api_url'] ) . $this->config['readme'] );

                if ( is_wp_error( $raw_response ) )
                    return $version;

                preg_match( '#^\s*`*~Current Version\:\s*([^~]*)~#im', $raw_response['body'], $__version );

                if ( isset( $__version[1] ) ) {
                    $version_readme = $__version[1];
                    if ( -1 == version_compare( $version, $version_readme ) )
                        $version = $version_readme;
                }

            }

            // refresh every 6 hours
            if ( false !== $version )
                set_site_transient( $this->config['slug'].'_new_version', $version, 60*60*6 );
        }

        return $version;
    }

This should speed up every site using this class, removing an unneeded call to the GitHub API.

I'm working on a proper pull request but wanted to share this to get feedback.