Add support for Linaro
Emergency workaround for salt issue 6502

This workaround will create the cachedir that 0.16.2 fails to (see
https://github.com/saltstack/salt/issues/6502)
Merge pull request #194 from terminalmage/cachedir-fix

Emergency workaround for salt issue 6502
Merge pull request #192 from terminalmage/linaro-fix

Add support for Linaro
Update ChangeLog to include the Linaro support added.
Bump version to 1.5.6
Add Linaro to the supported systems in the Readme file.
Fix syntax error from #194