Add slash and cut extension of file (nginx rules)

I tried to figure out how to add "/" to the end of every url. And this url need to be without extension. For example:

example.com/about.php; example.com/about.html => example.com/about/

I'm dummy in configuration nginx rewrite rules. This is my config:

server{
    root /usr/share/nginx/www/example.com;
    index index.php index.html index.htm;

    # Make site accessible from http://localhost/
    server_name example.com www.example.com;

    client_max_body_size 20M;

    # BEGIN W3TC Browser Cache
    gzip on;
    gzip_types text/css text/x-component application/x-javascript application/json  application/javascript text/javascript text/x-js text/richtext image/svg+xml text/plain text$;
    # END W3TC Browser Cache

    location /blog {
            # First attempt to serve request as file, then
            # as directory, then fall back to index.html
            # try_files $uri $uri/ /index.php;
            try_files $uri $uri/ /blog/index.php?q=$uri&$args;
            # Uncomment to enable naxsi on this location
            # include /etc/nginx/naxsi.rules
    }



    location ~* ^.+\.(rss|atom|jpg|jpeg|gif|png|ico|rtf|js|css|json)$ {
            expires max;
    }

    location ~ \.php$ {
            try_files $uri =404;
            fastcgi_split_path_info ^(.+\.php)(/.+)$;
            fastcgi_pass unix:/var/run/php5-fpm.sock;
            fastcgi_index index.php;
            include fastcgi_params;
    }

    location / {
        try_files $uri $uri.html $uri/ @extensionless-php;
        index index.php index.html index.htm;
    }

    location @extensionless-php {
        rewrite ^(.*)$ $1.php last;
    }

}

I founded some solutions but i can't to combine it, because I'm noob in nginx.

You need to change part of your config like that

location / {

                        rewrite ^(/.*[^/])\.(html|php)$ $1/ permanent;
                        rewrite ^(/.*[^/])(?!/)$ $1/ permanent;


                        try_files $uri $uri.html $uri/ @extensionless-php;
                        index index.php;

                }

                location @extensionless-php {
                   rewrite ^(.*)/$ $1.php last;
                }

First line rewrite ^(/.*[^/])\.(html|php)$ $1/ permanent; will redirect all requests with extensions .html or .php

rewrite ^(/.*[^/])(?!/)$ $1/ permanent;

Will add / to requests, which uri end without /