Upload builds to releases.parity.io (#1233)

* gitlab-ci.yml: upload binaries to s3

* gitlab-ci.yml: typo tag names

* gitlab-ci.yml: avoid dots in tags

* gitlab-ci.yml: try before_script

* gitlab-ci.yml: indentation

* gitlab-ci.yml: unified before_script

* gitlab-ci.yml: don't forget script

* use VERSION file

* build.sh only before builds

* git_strategy: none

* use own docker awscli image

* typo

* use artifacts folder

* enable uploads to s3 as well

* add builds.sh to tests