title: Change substrings of NSString to bold
body: <p>I have an <code>NSString</code>, that contains tags <code>[strong][\strong]</code>. Inside this tags, this words must be <strong>bold</strong> to be shown in a <code>UITextView</code> and then delete all the container tags once words are formatted,and I can't use an <code>UIWebView</code>. I think I must use <code>attributedString</code>s, but I'm not sure how can I achieve it.</p>