Make Links in description clickable

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- [x] I have verified there are no duplicate active or recent bugs, questions, or requests.
- [x] I have verified that I am using the latest version of MaterialStyledDialogs.
- [x] I have given my issue a non-generic title.
- [x] I have read over the [README](https://github.com/javiersantos/MaterialStyledDialogs/blob/master/README.md) and [Wiki](https://github.com/javiersantos/MaterialStyledDialogs/wiki) (before asking questions on how to do something).

###### Details
- MaterialStyledDialogs version: `2.1`

###### Reproduction Steps

Thanks for your library! I've been using the stock Android one until now and wanted to start using your project to get a nicer design for my dialogs, but unfortunately i can't get links in the dialog's body to be clickable.

With the stock dialog i used this to make them behave like you'd expect from a link:
```
((TextView) myDialog.findViewById(android.R.id.message))
.setMovementMethod(LinkMovementMethod.getInstance());
```

Any hints how to accomplish this / which ID to use? Maybe you could also add native support, like the original project: https://github.com/afollestad/material-dialogs/blob/master/core/src/main/java/com/afollestad/materialdialogs/DialogInit.java

Review README.md and the Wiki for the dialog API, then compare the linked afollestad material-dialogs DialogInit.java implementation with the reported LinkMovementMethod usage. Identify how MaterialStyledDialogs exposes its description text. Done means links in dialog descriptions are clickable as expected.

Written by the indexing model from the issue text.