created a basic makefile to install in /usr/include (#9)

* created a basic makefile to install in /usr/include

* fixed readme to explain make usage

* created a basic makefile to install in /usr/include

Makefile

@@ -0,0 +1,10 @@
+.PHONY: install
+
+install: conio.h
+	@test -f /usr/include/conio.h \
+		&& printf "/usr/include/conio.h already exists\n" \
+		|| true
+	@test -w /usr/include/ \
+		&& cp conio.h /usr/include/conio.h \
+		|| printf "Please run with elevated privileges\n" \
+

README.md

@@ -71,13 +71,7 @@ This is a library `conio.h` for linux. Just copy file and paste file `conio.h` o
 > ![Copy & Paste](https://github.com/zoelabbb/conio.h/blob/master/src/img/Copy%20%26%20Paste.png)
 
 ### Step 2 :
-
-- After you finish download file `conio.h`
-- Copy file `conio.h` :point_right: !! JUST COPY FILE NOT FOLDER !!
-- Go to `/usr/include/`
-- Right click on folder `/usr/include/`
-- Choose Open as Administrator (root)
-- Paste file `conio.h`
+- `sudo make install`
 - Restart or Close your IDE and open it again
 - And done :D