Filters improvement

[DumboOctopus]

In the home page, the filters on the right hand side can be improved:

1. ready to post includes post which have already been sent
2. The sent time should have 2 points you can drag: one point for lower bound, one for upperbound. e.g: You can search for all posts which are scheduled to be posted between 10 am and 1 pm. As of now, we just have one time point. So we can search for all posts scheduled after 10 am.
3. When the time filter is dragged to middle, it says 12 am instead of 12 pm.