Weekend Time/57 -- Don't display time on weekends

[Trello Card] (https://trello.com/c/HEihTyLf/57-weekend-schedule-don-t-display-times)

Students can choose to spread out the work over Sat/Sun as they please.

start_time will still be specified to facilitate ordering. The estimated duration should be displayed in it's place instead


Merge issues came up on [old pull request](https://github.com/lighthouse-labs/laser_shark/pull/55). Created new branch
There are three seperate `weekend?` checks in this partial. Kinda hard to follow. Try breaking it up into one check only please. Also, `unless` shouldn't have an `else` (general ruby style) If you are using an `else` use an `if` instead plz.