added string escaping

input.lisp

@@ -8,7 +8,9 @@
    4.0
    (dave
      1
+     "here's an escaped quote: \" how neat!!!"
      2
+     "and here's an escaped \\, sweet!"
      albert-camus
      3
      (sam 3 2 2)))

skeam.go

@@ -150,6 +150,17 @@ func lexString(l *lexer) (stateFn, error) {
 	case '"':
 		l.emit(str1ng)
 		return lexWhitespace, nil
+    case '\\':
+        return lexStringEsc, nil
+	}
+	l.append(r)
+	return lexString, nil
+}
+
+func lexStringEsc(l *lexer) (stateFn, error) {
+    r, err := l.next()
+    if err != nil {
+        return nil, err
     }
     l.append(r)
     return lexString, nil