Issue title: Unreachable code in timepicker
 Issue body: When building my app with webpack I get:
```
ERROR in ./~/ng2-bootstrap/components/timepicker/timepicker.ts
(112,5): error TS7027: Unreachable code detected.
```
Seems legit, because there is an `if (true)` with a `return` and code after that:
https://github.com/valor-software/ng2-bootstrap/blob/802c64f65b42ca8f9b6d5a184f229c19934ecbb6/components/timepicker/timepicker.component.ts#L103
 Comments: 
 Comment 0: You using ts 1.8 :)
 Comment 1: Whoops possible. Is 1.8 not yet supported?
 Comment 2: Is it out of beta? 
 Comment 3: I am really waiting for it, it may simplify system js bundling
 Comment 4: No it's not: https://github.com/Microsoft/TypeScript/releases
Shall I leave this issue open? Since the problem will occur in the future.
 Comment 5: updated description to contain angular blocker issue https://github.com/angular/angular/issues/6468
 Comment 6: fyi: blocker issue closed.
 Comment 7: Yeap, I know. But not available until Monday, in trip right now
 Comment 8: All good. Have a nice trip ;-).
 Comment 9: Thanks, when I am back, will updating all the things :)
{'source': 'GithubIssues', 'repo_name_with_owner': 'valor-software/ng2-bootstrap', 'issue_id': 130314770, 'repo_stars': 2644.0}