feat(html-content): generic template

[gilhanan]

Alternative for PR #64

• What kind of change does this PR introduce? Close: https://github.com/akserg/ng2-toasty/issues/3

• What is the current behavior? (You can also link to an open issue here) Not supporting 'html' content in toasts

• What is the new behavior (if this is a feature change)? Supporting ability to projecting 'html' templates in toasts

• Other information: Testings using this branch: ng2-webpack-demo/toasty-html-content

Using that code:

<ng2-toasty>
  <template toastyTemplate="title" let-toast>
    HTML title: <span style="background-color: #1EAEDB; color: #E1CB00;">{{toast.title}}</span>
  </template>
  <template toastyTemplate="message" let-toast>
    HTML message: <span style="background-color: #ff0039; color: #00e104;">{{toast.msg}}</span>
  </template>
</ng2-toasty>

Gives the result:

I would happy to review and discussing

[gilhanan]

Close by merging https://github.com/akserg/ng2-toasty/pull/65