[doc] fixed the horizontal form example

[javiereguiluz]

The original horizontal form example wasn't correctly displayed because it uses .col-lg- columns. Using .col-sm- columns fixes this problem:

In addition, the id attributes of the form controls have been fixed (inputEmail3 instead of inputEmail1, etc.).

[cvrebert]

In that case, it should use .col-xs-*.

[javiereguiluz]

@cvrebert I'm afraid that you cannot use .col-xs-* because the example uses column offsets and they aren't available for .col-xs-*

[cvrebert]

You seem to have changed the IDs of the inputs for no apparent reason.

[javiereguiluz]

Yes. At the end of my commit I've added the following:

In addition, the id attributes of the form controls have been fixed (inputEmail3 instead of inputEmail1, etc.).

The reason? The first form example uses inputEmail1, the second example uses inputEmail2. Being the third example, I found it reasonable to rename it to inputEmail3 (the same goes for the password form field).

[cvrebert]

Ah, right, damn. We plan on remedying that, but not sure when.