Bulma 0.7.4 Compatibility

Added:

• Fieldset component (with disabled prop)
• Button.Group size prop
• Tag.Group size prop
• Image.Container appends has-ratio to children when a "ratio-size" is used.

Changes:

• IMAGE_CONTAINER_DEFAULTS split sizes into dimmensions and ratios to better reflect Bulma structure.
• Progress no longer has default value prop = 0. I.e. it can now be an "indeterminate" progress bar.

Updated:

• Bulma 0.7.4