Add CHANGELOG and documentation for Linux support on Homebrew

Ref: go-task/homebrew-tap#1

Thanks @dawidd6

Author: andreynering

CHANGELOG.md

@@ -10,6 +10,8 @@
 - We now have a `--taskfile` flag (alias `-t`), which can be used to run
   another Taskfile (other than the default `Taskfile.yml`)
   ([#221](https://github.com/go-task/task/pull/221)).
+- It's now possible to install Task using Homebrew on Linux
+  ([go-task/homebrew-tap#1](https://github.com/go-task/homebrew-tap/pull/1)).
 
 ## v2.5.2 - 2019-05-11
 

docs/installation.md

@@ -8,13 +8,15 @@ The `task_checksums.txt` file contains the sha256 checksum for each file.
 
 ## Homebrew
 
-If you're on macOS and have [Homebrew][homebrew] installed, getting Task is
-as simple as running:
+If you're on macOS or Linux and have [Homebrew][homebrew] installed, getting
+Task is as simple as running:
 
 ```bash
 brew install go-task/tap/go-task
 ```
 
+> This installation method is only currently supported on amd64 architectures.
+
 ## Snap
 
 Task is available for [Snapcraft][snapcraft], but keep in mind that your