readme: add missing installation and usage sections

README.md

@@ -5,3 +5,43 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/avakarev/hashify)](https://goreportcard.com/report/github.com/avakarev/hashify)
 
 CLI utility to calculate file checksums
+
+## Installation
+
+#### macOS
+
+With [Homebrew](https://brew.sh/): `brew tap avakarev/tap && brew install hashify`
+
+### Binaries
+
+[Binaries](https://github.com/avakarev/hashify/releases) for Linux and macOS
+
+### From source
+
+Make sure you have a working Go environment (Go 1.12 or higher is required).
+See the [install instructions](http://golang.org/doc/install.html).
+
+Compiling `hashify` is easy, simply run:
+
+    git clone https://github.com/avakarev/hashify.git
+    cd hashify
+    make build
+
+## Usage
+
+    ○ $:> hashify -md5 -sha256 go.mod go.sum test/file
+    go.mod
+       md5 | 88e79e82744fd709ca1c5918f88fe9e9
+    sha256 | 03f3b24637f943604160573177815de6067c89c1993e38ea4d39595db246d51c
+
+    go.sum
+       md5 | 9073179bce05f8762267b2017ecd8e5c
+    sha256 | 270473f17ead3f907fda3372bfc3a4fed2a45f3527af79cb5d84fbec9c50cfbf
+
+    test/file
+       md5 | 8ddd8be4b179a529afa5f2ffae4b9858
+    sha256 | 03ba204e50d126e4674c005e04d82e84c21366780af1f43bd54a37816b6ab340
+
+## License
+
+`hashify` is licensed under MIT license. (see [LICENSE](./LICENSE))