Fix: escape character in string causes JS syntax error

Fix for issue #27.

Stop embedding strings directly into source code. Instead,
Convert strings into char array so that escape character won’t break syntax.

Before
```c++
auto var1 = JSStringCreateWithUTF8CString("constant");
```

After
```c++
const char var0[] = { 99,111,110,115,116,97,110,116,0 };
auto var1 = JSStringCreateWithUTF8CString(var0);
```