Create basic CLI interface

As of now, it is possible to feed lang-evolve-cli a set of rules as a
file, as well as an input as a file too. A `--help` option is provided
as well through Clap.

.gitignore

@@ -1 +1,4 @@
 /target
+*.log
+*.txt
+*.yaml

Cargo.toml

@@ -8,3 +8,4 @@ edition = "2018"
 
 [dependencies]
 lang-evolve-core = { path = "../lang-evolve-core"}
+clap = "3.0.0-beta.1"

src/main.rs

@@ -1,3 +1,21 @@
+use std::fs::File;
+use std::io::prelude::*;
+
+use lang_evolve_core::settings::Settings;
+
+mod opts;
+use opts::Opts;
+use clap::Clap;
+
 fn main() {
-    println!("Hello, world!");
+    lang_evolve_core::init().unwrap();
+
+    let opts: Opts = Opts::parse();
+    let settings = Settings::from(opts.settings).unwrap();
+    let mut input_file = File::open(opts.input).unwrap();
+    let mut input = String::new();
+    input_file.read_to_string(&mut input).unwrap();
+
+    println!("{:?}", settings);
+    println!("{}", settings.apply(input).unwrap());
 }

src/opts.rs

@@ -0,0 +1,11 @@
+use clap::Clap;
+
+#[derive(Clap, Debug)]
+#[clap(version = "0.1", author = "Lucien \"Phundrak\" Cartier-Tilet <lucien@phundrak.com>")]
+pub struct Opts {
+    #[clap(short, long)]
+    pub input: String,
+
+    #[clap(short, long)]
+    pub settings: String,
+}