Ignore build-related files in "git archive" (fixes #8167)

This is useful for keeping standard "composer create-project"
checkouts clean. Unless they use "--keep-vcs", in which case
.gitattributes is (correctly) ignored.

This has the side effect that archive-checkouts can't
run phing or phpunit scripts, but I think that's
acceptable.
IIS 7.5 does not like forward slash at the end of silverstripe-cache

IIS 7.5 does not like forward slash at the end of silverstripe-cache
Merge pull request #32 from sunnysideup/patch-1

IIS 7.5 does not like forward slash at the end of silverstripe-cache
Merge pull request #29 from chillu/pulls/gitattributes

Ignore build-related files in "git archive" (fixes #8167)
Remove require-dev section, composer doesn't handle it well

Any "composer require <module>" call will first call
a "composer update". This *automatically* includes dev requirements,
without providing a way to turn off this behaviour.
A workaround would be "composer require --no-update <module> && composer update --no-dev <module>",
but that drastically reduces the usefulness of the command
for our target audience (moderately technical devs).

In the end, the small faction of devs needing the dev dependencies
also know how to install them on their own. And having a local phpunit
build actually gets in the way more than it helps in case you have
it installed through PEAR already (can get really weird when using the
PEAR provided "phpunit" binary, but the autoloader finds the composer managed classes).
Merge pull request #36 from chillu/pulls/require-dev

Remove require-dev section, composer doesn't handle it well
Updated behat.yml to reflect changes in behat-extension module
Merge remote-tracking branch 'origin/3.0' into 3.1