Fix styling issues

[shrirambalaji]

Hey!

This PR fixes some styling issues detailed below.

Changes:

• The Thumbnail now covers the entire div, without looking stretched.
• A semi-transparent circle background has been added for the ❤️ and 👁 icons to be more visible

• The styling for the Hide Viewed Toggle component has been modified.

• Some minor styling fixes in Speaker component

PS: The commit history is sort of a mess, because I realised a test was failing after a commit. Fixed later. Sorry 🤦‍♂️

Btw, the travis build is taking too long and fails with an error.

unhandledRejection { status: 401,
  error: 
   { message: 'Bad credentials',
     documentation_url: 'https://developer.github.com/v3' } }
unhandledRejection { status: 401,

I'm not aware of the deployment details, just letting you folks know.

[SaraVieira]

Heyy !

THis looks awesome ! I will merge and also deploy it today :D

About the build don't worry about it, it's the deploy that fails because I have tokens for github and now and those are not shared when forked but it will work when merged !

Thank you again for making this awesomer 🎉🚀