Fix tests and comments

examples/hello_world.fx

@@ -1,3 +1,5 @@
+// This is a comment
+
 fn main() {
     return 1;
     

src/lexer/tests.rs

@@ -141,7 +141,7 @@ mod tests {
             Token {
                 len: 6,
                 kind: TokenKind::Comment,
-                raw: "-- foo".to_owned(),
+                raw: "// foo".to_owned(),
             }
         );
 

src/parser/mod.rs

@@ -16,7 +16,7 @@ impl Parser {
         // FIXME: Fiter without collecting?
         let tokens_without_whitespace: Vec<Token> = tokens
             .into_iter()
-            .filter(|token| token.kind != TokenKind::Whitespace)
+            .filter(|token| token.kind != TokenKind::Whitespace && token.kind != TokenKind::Comment)
             .collect();
         Parser {
             tokens: tokens_without_whitespace.into_iter().peekable(),