Add basic main, update gitignore & READM

.gitignore

@@ -1,13 +1,2 @@
-# ---> Rust
-# Compiled files
-*.o
-*.so
-*.rlib
-*.dll
-
-# Executables
-*.exe
-
-# Generated by Cargo
-/target/
-
+/.idea/
+/main

README.md

@@ -1,2 +1,13 @@
-# 01-hello-world
+# 01 - Hello world
 
+## Build
+
+```
+rustc main.rs
+```
+
+## Run
+
+```
+./main
+```

main.rs

@@ -0,0 +1,3 @@
+fn main() {
+    println!("Hello world!");
+}