Update validators.md

[smdwireless]

Added: de.paywith.glass
Updated Contact: paywith.glass
Removed: tradedirect.io

[rice2000]

I'm going to go ahead and merge this, but wanted to point out that this list isn't really kept up to date, and that it will likely be deprecated in the not-too-distant future.

Instead of relying on a central list of validators, we now ask validators to self identify by implementing SEP-20:
https://github.com/stellar/stellar-protocol/blob/master/ecosystem/sep-0020.md

Doing so allows them to verify their own identities, and ensures they'll show up correctly in network explorers like stellarbeat:
https://stellarbeat.io/