move more_btn to components and use flex to center it

[chenkaiC4]

just move more_btn to independent component, and use flex to center it.

[chenkaiC4]

@AdamBrodzinski I find a bug, when click more btn, now 5 feed items will be added to feed list, but the comments of these 5 new feed items don't display. when add a new comment or click 'like', these comments will display。I will look into this bug, and create a new PR.

[AdamBrodzinski]

Sounds good. I think what may help too is to breakup the subscription into two subscriptions... the post and the post comments. I think I remember there being some weird buggy behavior with rendering comments.