The sha256 for README.md seems to have changed.
The sha256 for README.md seems to have changed.

Installing xorg-protocols as a prereq to installing R failed (CentOS 7, `HOMEBREW_BUILD_FROM_SOURCE=1`).

```
[throgg@builder apps]$ brew install r
==> Installing r from homebrew/science
==> Installing dependencies for homebrew/science/r: xorg-protocols, libxau, xcb-proto, libxdmcp, gettext, homebrew/dupes/m4, bison, \
flex, doxygen
==> Installing homebrew/science/r dependency: xorg-protocols
==> Downloading https://raw.githubusercontent.com/Linuxbrew/homebrew-xorg/master/README.md
Already downloaded: /home/throgg/.cache/Homebrew/xorg-protocols-latest.md
Error: SHA256 mismatch
Expected: 846477dd316964fe52e9f73c3752d3c0383f7099046dd06ddfda92c2f9baad5d
Actual: 7d5cca1b4bdc2a3aefe2ef7fedf919ea8fe4f907493d5d31661c5f8fa81a3161
Archive: /home/throgg/.cache/Homebrew/xorg-protocols-latest.md
To retry an incomplete download, remove the file above.
[throgg@builder apps]$
```

Replacing the Expected value of the sha256 in the formula with the actual allowed the build to proceed.

I grabbed the README.md using curl, verified that it's sha256 was what the install step found, and scanned the file by eye.  It seems ok.

Closes Linuxbrew/homebrew-xorg#139.

Signed-off-by: Bob W. Hogg <c772a964fd55352a3510e5d535dd9ccc9ac30168@linux.com>

Linuxbrew/homebrew-xorg,LinuxbrewTestBot/homebrew-xorg,maxim-belkin/homebrew-xorg