Merge pull request #3 from ggerman/feature/add-instalation-to-readme

install instructions

Author: ggerman

README.md

@@ -1,2 +1,21 @@
 # imprint
 Secure, signed image rendering for Rails
+
+## Installation
+
+### System dependencies
+
+```bash
+Ubuntu:
+sudo apt install libgd-dev
+```
+
+macOS:
+```bash
+brew install gd
+```
+
+### Gemfile
+```bash
+gem 'imprint'
+```