Implement Caption creation component

[zxkevin]

As an account holder I want a page for creating a Caption for each Post, so that others can see my funny caption for the image.

Acceptance Criteria:

• Text fields for each specific post as well as button for submission.
• When a user clicks on the submit button whatever they typed in the captions box will be uploaded. Currently, users can submit captions anonymously.
• Create the Caption creation component.

Tasks:

• [x] Create a Create captions component. /Cyrus
• [x] Create a textfield and submission button for each post. /Cyrus & Ari
• [x] Page gives a response if the caption got submitted successfully after the submission button is clicked. /Cyrus & Ari
• [x] Display the image of the post being captioned at the top of the page. /Ari

[sjiang1]

Can you submit a caption without login? What happens if a user submits without login? Please add this to your acceptance criteria.

[3dxp]

Currently users of the site will be able to submit captions on posts anonymously.

[ahassani93]

Updated the acceptance criteria to include a note on caption creation without login.

[ahassani93]

Changed "page" to "component" because of duplicate tasks with issue #44.