added "offset" option

[lnx85]

Use offset: { left: , top: } to shift info window position left and top.

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed, please reply here (e.g. I signed it!) and we'll verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please let us know the company's name.

[lnx85]

I signed it as VarDump s.r.l. (using staff@var-dump.it)

Il 02/03/16 17:26, googlebot ha scritto:

Thanks for your pull request. It looks like this may be your first
contribution to a Google open source project. Before we can look at
your pull request, you'll need to sign a Contributor License Agreement
(CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed, please reply here (e.g. |I signed it!|) and we'll
verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your
  GitHub username or you're using a different email address. Check
  your existing CLA data https://cla.developers.google.com/clas
  and verify that your email is set on your git commits
  https://help.github.com/articles/setting-your-email-in-git/.
• If you signed the CLA as a corporation, please let us know the
  company's name.

—
Reply to this email directly or view it on GitHub
#24 (comment).

[mpcallahan]

InfoWindowOptions already has a "pixelOffset" property that references a Size type.
https://developers.google.com/maps/documentation/javascript/3.exp/reference#InfoWindowOptions

I'd suggest updating the code to use this, or at least use the same naming (i.e. using "pixelOffset" instead of just "offset" as well as Size's "width"/"height" properties instead of "left"/"top") this would make porting from InfoWindow to InfoBubble easier.