Rename BrowserID-Version header to BrowserID-git-sha

fixes #3125
Fix button width in "Is this your computer" not keeping up with screen resize.

jQuery changed the way to remove a manually set CSS style. We did not keep up when we updated jQuery. Now we do.

fixes #2066
Convert the last remaining "BrowserID-Version"s to "BrowserID-git-sha"s
recognize windows 8 and NT 5.0
Merge pull request #3201 from jrgm/issue3187-windows8

recognize windows 8 and NT 5.0
Add KPI load testing docs

    These used to live at https://gist.github.com/kparlante/5054439/
    and might be useful, so let's add 'em to the docs folder
Explicitly list default for parallel execution of tests
Put the default for -p in the right place.
Merge pull request #3204 from karlht/issue3174

Explicitly list default for parallel execution of tests
Merge pull request #3203 from 6a68/add_load_testing_docs

Add KPI load testing docs

Thanks @6a68!
Merge pull request #3183 from mozilla/issue_2066_button_width

Fix button width in "Is this your computer" not keeping up with screen resize.
Merge pull request #3149 from mozilla/issue_3125_version_header_name

Rename BrowserID-Version header to BrowserID-git-sha