This issue is caused in Laravel 5.4 by the database version.

According to the docs (in the Index Lengths & MySQL / MariaDB section):

Laravel uses the utf8mb4 character set by default, which includes support for storing "emojis" in the database. If you are running a version of MySQL older than the 5.7.7 release or MariaDB older than the 10.2.2 release, you may need to manually configure the default string length generated by migrations in order for MySQL to create indexes for them. You may configure this by calling the Schema::defaultStringLength method within your AppServiceProvider.

In other words, in <ROOT>/app/Providers/AppServiceProvider.php:

// Import Schema
use Illuminate\Support\Facades\Schema;
// ...

class AppServiceProvider extends ServiceProvider
{

public function boot()
{
    // Add the following line
    Schema::defaultStringLength(191);
}

// ...

}

But as the comment on the other answer says:

Be careful about this solution. If you index email fields for example, stored emails can only have a max length of 191 chars. This is less than the official RFC states.

So the documentation also proposes another solution:

Alternatively, you may enable the innodb_large_prefix option for your database. Refer to your database's documentation for instructions on how to properly enable this option.

In the AppServiceProvider.php,you include this code top of the file.

use Illuminate\Support\Facades\Schema;

And you add this code in boot method.

 Schema::defaultStringLength(191);

For someone who don't want to change AppServiceProvider.php. (In my opinion, it's bad idea to change AppServiceProvider.php just for migrateion)

You can add back the data length to the migration file under database/migrations/ as below:

create_users_table.php

$table->string('name',64);
$table->string('email',128)->unique();

create_password_resets_table.php

$table->string('email',128)->index();

I don't know why the above solution and the official solution which is adding

Schema::defaultStringLength(191);

in AppServiceProvider didn't work for me. What worked for was editing the database.php file in config folder. Just edit

'charset' => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',

to

'charset' => 'utf8',
'collation' => 'utf8_unicode_ci',

and it should work. Hope it helps.

Instead of setting a limit on lenght I think this is better , what is perfectly work for me :)

Inside

config/database.php

replace this line for mysql

'engine' => 'InnoDB ROW_FORMAT=DYNAMIC',

upon

'engine' => null,

If you want to change in AppServiceProvider then you need to define the length of email field in migration. just replace the first line of code to the second line.

create_users_table 

$table->string('email')->unique();
$table->string('email', 50)->unique();

create_password_resets_table

$table->string('email')->index();
$table->string('email', 50)->index();

After successfully changes you can run the migration.
Note: first you have to delete (if you have) users table, password_resets table from the database and delete users and password_resets entries from migration table.