Return a comma separated string of all the pagination links

I liked the gem but I wanted a way to have just a comma separated list of pagination urls for my api so I add an `all:` option. Example `paginate json: User.all, per_page: 5, all: true`. This will return a string as follows.
```
"<http://0.0.0.0:3001/api/v1/users?page=2>, <http://0.0.0.0:3001/api/v1/users?page=3>, <http://0.0.0.0:3001/api/v1/users?page=4>, <http://0.0.0.0:3001/api/v1/users?page=5>, <http://0.0.0.0:3001/api/v1/users?page=6>, <http://0.0.0.0:3001/api/v1/users?page=7>, <http://0.0.0.0:3001/api/v1/users?page=8>, <http://0.0.0.0:3001/api/v1/users?page=9>, <http://0.0.0.0:3001/api/v1/users?page=10>, <http://0.0.0.0:3001/api/v1/users?page=11>, <http://0.0.0.0:3001/api/v1/users?page=12>, <http://0.0.0.0:3001/api/v1/users?page=13>, <http://0.0.0.0:3001/api/v1/users?page=14>, <http://0.0.0.0:3001/api/v1/users?page=15>, <http://0.0.0.0:3001/api/v1/users?page=16>, <http://0.0.0.0:3001/api/v1/users?page=17>, <http://0.0.0.0:3001/api/v1/users?page=18>, <http://0.0.0.0:3001/api/v1/users?page=19>, <http://0.0.0.0:3001/api/v1/users?page=20>, <http://0.0.0.0:3001/api/v1/users?page=21>, <http://0.0.0.0:3001/api/v1/users?page=22>, <http://0.0.0.0:3001/api/v1/users?page=23>, <http://0.0.0.0:3001/api/v1/users?page=24>, <http://0.0.0.0:3001/api/v1/users?page=25>, <http://0.0.0.0:3001/api/v1/users?page=26>, <http://0.0.0.0:3001/api/v1/users?page=27>, <http://0.0.0.0:3001/api/v1/users?page=28>, <http://0.0.0.0:3001/api/v1/users?page=29>, <http://0.0.0.0:3001/api/v1/users?page=30>, <http://0.0.0.0:3001/api/v1/users?page=31>, <http://0.0.0.0:3001/api/v1/users?page=32>, <http://0.0.0.0:3001/api/v1/users?page=33>, <http://0.0.0.0:3001/api/v1/users?page=34>, <http://0.0.0.0:3001/api/v1/users?page=35>, <http://0.0.0.0:3001/api/v1/users?page=36>, <http://0.0.0.0:3001/api/v1/users?page=37>, <http://0.0.0.0:3001/api/v1/users?page=38>, <http://0.0.0.0:3001/api/v1/users?page=39>, <http://0.0.0.0:3001/api/v1/users?page=40>, <http://0.0.0.0:3001/api/v1/users?page=41>, <http://0.0.0.0:3001/api/v1/users?page=42>, <http://0.0.0.0:3001/api/v1/users?page=43>, <http://0.0.0.0:3001/api/v1/users?page=44>, <http://0.0.0.0:3001/api/v1/users?page=45>, <http://0.0.0.0:3001/api/v1/users?page=46>, <http://0.0.0.0:3001/api/v1/users?page=47>, <http://0.0.0.0:3001/api/v1/users?page=48>, <http://0.0.0.0:3001/api/v1/users?page=49>, <http://0.0.0.0:3001/api/v1/users?page=50>, <http://0.0.0.0:3001/api/v1/users?page=51>, <http://0.0.0.0:3001/api/v1/users?page=52>, <http://0.0.0.0:3001/api/v1/users?page=53>, <http://0.0.0.0:3001/api/v1/users?page=54>, <http://0.0.0.0:3001/api/v1/users?page=55>, <http://0.0.0.0:3001/api/v1/users?page=56>, <http://0.0.0.0:3001/api/v1/users?page=57>, <http://0.0.0.0:3001/api/v1/users?page=58>, <http://0.0.0.0:3001/api/v1/users?page=59>, <http://0.0.0.0:3001/api/v1/users?page=60>, <http://0.0.0.0:3001/api/v1/users?page=61>, <http://0.0.0.0:3001/api/v1/users?page=62>, <http://0.0.0.0:3001/api/v1/users?page=63>, <http://0.0.0.0:3001/api/v1/users?page=64>, <http://0.0.0.0:3001/api/v1/users?page=65>, <http://0.0.0.0:3001/api/v1/users?page=66>, <http://0.0.0.0:3001/api/v1/users?page=67>, <http://0.0.0.0:3001/api/v1/users?page=68>, <http://0.0.0.0:3001/api/v1/users?page=69>, <http://0.0.0.0:3001/api/v1/users?page=70>, <http://0.0.0.0:3001/api/v1/users?page=71>, <http://0.0.0.0:3001/api/v1/users?page=72>, <http://0.0.0.0:3001/api/v1/users?page=73>, <http://0.0.0.0:3001/api/v1/users?page=74>"

```