Change test to workaround babylon bug (#184)

Babylon has a bug where it doesn't escape DirectiveLiteral properly. Except for `'use strict';`, this never happens in real world code, so let's put strings in a array in order to workaround this bug and have the same output on both parsers.

https://github.com/babel/babylon/issues/289

tests/strings/__snapshots__/jsfmt.spec.js.snap

@@ -1,46 +1,44 @@
 exports[`test strings.js 1`] = `
-"\"abc\"
-\'abc\'
+"[
+  \"abc\",
+  \'abc\',
 
-\'\\\'\'
+  \'\\\'\',
 
-\'\"\'
-\'\\\"\'
-\'\\\\\"\'
+  \'\"\',
+  \'\\\"\',
+  \'\\\\\"\',
 
-\"\'\"
-\"\\\'\"
-\"\\\\\'\"
+  \"\'\",
+  \"\\\'\",
+  \"\\\\\'\",
 
-\"\'\\\"\"
-\'\\\'\"\'
+  \"\'\\\"\",
+  \'\\\'\"\',
 
-\'\\\\\'
-\"\\\\\"
+  \'\\\\\',
+  \"\\\\\",
 
-\'\\0\'
-\'🐶\'
+  \'\\0\',
+  \'🐶\',
+];
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-\"abc\";
-\"abc\";
-
-\"\'\";
-
-\'\"\';
-\'\"\';
-\'\\\\\"\';
-
-\"\'\";
-\"\'\";
-\"\\\\\'\";
-
-\"\'\\\"\";
-\"\'\\\"\";
-
-\"\\\\\";
-\"\\\\\";
-
-\"\\u0000\";
-\"🐶\";
+[
+  \"abc\",
+  \"abc\",
+  \"\'\",
+  \'\"\',
+  \'\"\',
+  \'\\\\\"\',
+  \"\'\",
+  \"\'\",
+  \"\\\\\'\",
+  \"\'\\\"\",
+  \"\'\\\"\",
+  \"\\\\\",
+  \"\\\\\",
+  \"\\u0000\",
+  \"🐶\"
+];
 "
 `;

tests/strings/strings.js

@@ -1,21 +1,23 @@
-"abc"
-'abc'
+[
+  "abc",
+  'abc',
 
-'\''
+  '\'',
 
-'"'
-'\"'
-'\\"'
+  '"',
+  '\"',
+  '\\"',
 
-"'"
-"\'"
-"\\'"
+  "'",
+  "\'",
+  "\\'",
 
-"'\""
-'\'"'
+  "'\"",
+  '\'"',
 
-'\\'
-"\\"
+  '\\',
+  "\\",
 
-'\0'
-'🐶'
+  '\0',
+  '🐶',
+];