Users can review announcements & pitches independently of each other

Trello: https://trello.com/c/Kpu0RH61/60-users-can-view-pitches-announcements

NOTES: I want users to have the freedom to view pitches and announcements independently of each other. This enables to the user to view all pitches or all announcements belonging to them. 
This results in indexes to sometimes display all data or filtered data depending on which route they're coming through. 
One challenge this direction presents is forcing the user to now specify extra information in forms. If a user wants to create a new pitch and comes from /pitches, it makes sense for them to specify which client announcement. However, if the user is coming from announcements/3/pitches, I'd (at the very least) like for the drop-down menu to be pre-set to the announcement name. I will look to do this (and a few other refactor-ings) in a future PR.

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