write icc files to tmp only when necessary

[code1super]

I see no reason to write these files to a temporary file when it is not consumed. It can make unnecessary errors when there is no have temporary folder or when there is no disk space or when there are no write permissions.

[tonimelisma]

Thanks @code1super and apologies for the delay, I've been traveling overseas. Could you write tests for the changes please?

The PR is greatly appreciated!

[coveralls]

coverage: 73.196% (-0.4%) from 73.557% when pulling 9613e3efddb8e7d6c7f510f27c67e3623b006731 on code1super:write-when-necessary into 0c98a287803d8c24539b9bfdbdf361a337343ef9 on davidbyttow:master.

[tonimelisma]

Hey @code1super I love the PR but could you add the tests?

[rhafer]

@tonimelisma @code1super I just created #456 which contains @code1super's original commits plus adjustments to the test. I hope that's fine.