Adding `$table->rememberToken()` docs.

This can be merged with https://github.com/laravel/framework/pull/4622

Signed-off-by: Adam Engebretson <adam@enge.me>
Merge pull request #817 from adamgoose/4.2

Adding `$table->rememberToken()` docs.
make note on pagination and group by.
Merge branch '4.2'