Optional btn & input font family

[MartijnCuppens]

Optional font family for .btns and .form-controls. Doesn't generate any css by default.

[mdo]

We'll want to check the default font stacks for some older browsers. I can't remember for certain anymore, but I feel like some weren't inheriting their fonts in inputs and buttons.

[MartijnCuppens]

@mdo, I guess this is already fixed in reboot:

bootstrap/scss/_reboot.scss

Lines 313 to 322 in e65dccf

	input,
	button,
	select,
	optgroup,
	textarea {
	margin: 0; // Remove the margin in Firefox and Safari
	font-family: inherit;
	font-size: inherit;
	line-height: inherit;
	}

[mdo]

Well then, awesome! 😆