Done using isort[1], with the following command:
```
isort -rc ./app ./tests
```
Adds linting to the `run_tests.sh` script to stop badly-sorted imports
getting re-introduced.
Chosen style is ‘Vertical Hanging Indent’ with trailing commas, because
I think it gives the cleanest diffs, eg:
```
from third_party import (
lib1,
lib2,
lib3,
lib4,
)
```
1. https://pypi.python.org/pypi/isort
Both `<button type='submit'>Submit<button>` and
`<input type='submit' value='Submit'>` can be used to submit a form.
We have historically[1] used `<input>` because it’s better-supported by
IE6 in that:
- the `submit` attribute is mandatory on `<button>`, not on `<input>`
- the `innerHTML` of a button will be submitted to the server, not the
value (as in other browsers)
Reasons to now use `<button>` instead:
- IE6/7 support is no longer a concern (especially with deprecation of
TLS 1.0 on the way)
- Because an `<input>` element can’t have children, the pseudo-element
hack[2] used to ensure the top edge of the button is clickable doesn’t
work. We’re seeing this bug[3] affect real users in research.
1. We inhereted our buttons from Digital Marketplace, here is me making
that change in their code: 8df7e2e79e (diff-b1420f7b7a25657d849edf90a70ef541)
2. 24e1906c0d (diff-ef0e4eb6f1e90b44b0c3fe39dce274a4R79)
3. https://github.com/alphagov/govuk_elements/issues/545
