🔧 popup: allow passing any props, but filter them so they wouldn't leak into DOM element

✔️ fix some props leaking into DOM-elements in select, popup and tabs components causing warning in react@15.2.0

🔧 rename LabelGroup into FieldGroup with minor internal changes
➕ add Label component

✔️ fix missing index.js in v0.4.3 (caused by npm bug npm/npm#5082)

✔️ revert changes from v0.4.2. Current onClick behavior is intentional, to let user focus (ex: input) or trigger (ex: checkbox, radio) form element. If you have something complex inside label-group, you probably should use different component.

✔️ fix label-group having label tag instead of div which caused weird onClick behaviour

✔️ tabs: fix exception on tab click when onTabChange handler is not specified

♻️ remove redundant dependencies which are not used anymore (component-uid, eventemitter3)

🔧 button: value prop is an empty string by default (fixes #5)
♻️ bump reBEM

➕ button: support for optional type prop