Remove package managers from README
I think we've been dropped from most of these since we haven't done a stable release in so long, and 2.1.1 depends on old versions of generally unsupported software (including the Redis library)
@@ -20,16 +20,7 @@ Installation
------------
The latest stable release of ZMap is version 2.1.1 and supports Linux, macOS, and
-BSD. It can be installed through the built-in package managers on the following
-operating systems:
-
-| OS | |
-| ----------------------------------------- | --------------------------- |
-| Debian and Ubuntu | `sudo apt install zmap` |
-| Fedora, CentOS, and RHEL | `sudo yum install zmap` |
-| Gentoo | `sudo emerge zmap` |
-| macOS (using [Homebrew](https://brew.sh)) | `brew install zmap` |
-| Arch Linux | `sudo pacman -S zmap` |
+BSD. We recommend installing ZMap from HEAD rather than using a distro package manager.
**Instructions on building ZMap from source** can be found in [INSTALL](INSTALL.md).
