Remove references to BitHub (signalapp#1576)

As of signalapp/Signal-Android@258910504cc2, BitHub is not working
anymore.

.github/PULL_REQUEST_TEMPLATE.md

@@ -10,7 +10,6 @@
 - [ ] My changes are rebased on the latest master branch
 - [ ] My commits are in nice logical chunks
 - [ ] I have followed the [best practices](http://chris.beams.io/posts/git-commit/) in my commit messages
-- [ ] I have made the choice whether I want the [BitHub reward](https://github.com/WhisperSystems/Signal-Android/wiki/BitHub-Rewards) or not by omitting or adding the word `FREEBIE` in my Git commit messages
 - [ ] I have tested my contribution on these platforms:
  * GNU Hurd 1.0, Chrom{e,ium} X.Y.Z
  * Amiga OS 3.1, Chrom{e,ium} Z.Y

README.md

@@ -31,18 +31,11 @@ Please see
 for setup instructions and contributor guidelines. And don't forget to sign the
 [CLA](https://whispersystems.org/cla/).
 
-This repository is set up with [BitHub](https://whispersystems.org/blog/bithub/), so you can make money for committing to Signal. The current BitHub price for an accepted pull request is:
-
-[![Current BitHub Price](https://bithub.herokuapp.com/v1/status/payment/commit/)](https://whispersystems.org/blog/bithub/)
-
-
 ## Contributing Ideas
 Have something you want to say about Open Whisper Systems projects or want to be part of the conversation? Get involved in the [community forum](https://whispersystems.discoursehosting.net)!
 
 ## Contributing Funds
-[![Donate](https://cloud.githubusercontent.com/assets/3121306/11278543/d46e03d0-8eeb-11e5-9691-0da1bf643192.png)](https://www.coinbase.com/checkouts/51dac699e660a4d773216b5ad94d6a0b)
-
-You can add funds to [BitHub](https://whispersystems.org/blog/bithub/) to directly help further development efforts.
+You can donate to Signal development through the [Freedom of the Press Foundation](https://freedom.press/crowdfunding/signal/).
 
 ## Cryptography Notice