Label fixes

[dariusrosendahl]

Issue description: #6

How to test:

• Checkout this branch
• cd castlecss-forms
• npm link
• cd ..
• Checkout the feature/castlecss-forms branch in https://github.com/CastleCSS/castlecss-docs/tree/feature/castlecss-forms
• cd castlecss-docs
• Install the project with npm i
• npm link castlecss-forms -S
• Build the project with npm run start
• Test!

[basmulderdnz]

Seems to be working, except that the label-above and label-blow classes have been functionally switched

[gbeumer]

Looks great.

3 issues:

• Select has default arrow up
• .label-above has disappeared
• textarea still has a vertically centered label