Work even when 'fs' not available for require;

and don't let webpack trip on it either (by using string variable as require argument which prevents static analysis/bundling failure).

lib/html-to-text.js

@@ -1,4 +1,14 @@
-var fs = require('fs');
+var fs;
+try {
+  var fsStr = 'fs'; // helps with webpack
+  fs = require(fsStr);
+} catch(e) {
+  fs = {
+    readFile: function(file, enc, callback) {
+      callback('failed to require fs');
+    }
+  };
+}
 var util = require('util');
 
 var includes = require('lodash/includes');