Add install script for Linux AMD64 (#8)

* Add install script for linux

* Add install instruction to README

README.md

@@ -34,13 +34,20 @@ commands in order to skip the above resources to possibly resolve the
 
 ## How to install
 
-### Direct download for Linux (64-bit)
+### Direct download for Linux (AMD64)
 
-The most straightforward way is to visit
-<https://github.com/guangie88/terraform-zap/releases>
-and download the latest version of statically built binary in the zip asset. The
-zip file is named as `terraform-zap-vX.Y.Z.zip`, and is currently meant only for
-any Linux 64-bit machine.
+The easiest way is to run the install script using shell as shown below.
+
+```bash
+curl -sSf https://raw.githubusercontent.com/guangie88/terraform-zap/master/install-index.sh | sudo sh
+```
+
+You will need to run as `root`, or run via `sudo`, since the script will place
+`terraform-zap` binary file into `/usr/local/bin/`.
+
+You may also choose to visit
+[releases](https://github.com/guangie88/terraform-zap/releases)
+and download the latest version of statically built binary in the zip asset.
 
 ### Via `cargo install`
 

install-linux.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env sh
+if [ `id -u` != 0 ]; then
+    echo "Run the script as root/sudo!"
+    exit 1
+fi
+
+REPO_USERNAME=guangie88
+REPO_NAME=terraform-zap
+
+LATEST_TAG=$(curl -sSf "https://api.github.com/repos/$REPO_USERNAME/$REPO_NAME/releases/latest" \
+    | grep tag_name \
+    | sed -n 's/.*"\(v.*\)".*/\1/p')
+
+BINARY_FILE=terraform-zap
+ZIP_FILE=$BINARY_FILE-$LATEST_TAG.zip
+BIN_DIR=/usr/local/bin
+
+# unzip cannot work on Unix pipe
+echo "Downloading '"$ZIP_FILE"'..."
+curl -sSfLO "https://github.com/guangie88/terraform-zap/releases/download/$LATEST_TAG/$ZIP_FILE"
+
+echo "Unzipping..."
+unzip -qq "$ZIP_FILE" 
+rm "$ZIP_FILE"
+
+echo "Moving binary file '"$BINARY_FILE"' to $BIN_DIR/..."
+mv $BINARY_FILE $BIN_DIR/
+chmod +x $BIN_DIR/$BINARY_FILE
+
+echo "DONE!\n\nterraform-zap requires terraform, be sure to place terraform in PATH.\n"