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

@@ -150,11 +150,22 @@ 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
+}
+
 // lex an integer.  Once we're on an integer, the only valid characters are
 // whitespace, close paren, a period to indicate we want a float, or more
 // digits.  Everything else is crap.