Form input focus state

Adds form focus state to all form elements (excluding `input[type="range"]`), including `.form__input-container`.

Do we have the outline on *every* element or just on free text inputs?

Screen grabs:
![screen shot 2014-06-30 at 14 01 06](https://cloud.githubusercontent.com/assets/1579511/3429915/a27c7c00-005b-11e4-970e-cf02c4346d9b.png)
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![screen shot 2014-06-30 at 14 00 59](https://cloud.githubusercontent.com/assets/1579511/3429917/a27d0dd2-005b-11e4-82fa-4ca7e934b4ee.png)
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![screen shot 2014-06-30 at 14 00 51](https://cloud.githubusercontent.com/assets/1579511/3429918/a27d6bba-005b-11e4-89b9-c831cd0581a3.png)
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![screen shot 2014-06-30 at 11 18 43](https://cloud.githubusercontent.com/assets/1579511/3429916/a27cc642-005b-11e4-8999-56c81d473ff1.png)
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![screen shot 2014-06-30 at 14 04 13](https://cloud.githubusercontent.com/assets/1579511/3429919/aaf0b734-005b-11e4-9630-83d513c85342.png)
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![screen shot 2014-06-30 at 14 01 26](https://cloud.githubusercontent.com/assets/1579511/3429920/aaf25bf2-005b-11e4-9400-5be0d878e6ce.png)
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![screen shot 2014-06-30 at 14 01 22](https://cloud.githubusercontent.com/assets/1579511/3429921/aaf39b66-005b-11e4-9cdd-54b640eab9c0.png)
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![screen shot 2014-06-30 at 14 01 16](https://cloud.githubusercontent.com/assets/1579511/3429922/aaf569be-005b-11e4-9fe1-7dc9ec2a6d1e.png)