Add defaults for environment variables

So we don't have to keep setting them for each CI and every single step
since there doesn't seem to be a way to share them between steps in
Drone.

.travis.yml

@@ -4,14 +4,6 @@ node_js:
 services:
   - docker
 
-before_install:
-  - export MAJOR_VERSION="2"
-  - export VSCODE_VERSION="1.41.1"
-  - export VERSION="$MAJOR_VERSION.$TRAVIS_BUILD_NUMBER"
-  - export TAG="$VERSION-vsc$VSCODE_VERSION"
-  - if [[ "$TRAVIS_BRANCH" == "master" ]]; then export MINIFY="true"; fi
-  - if [[ "$TRAVIS_BRANCH" == "master" ]]; then export PACKAGE="true"; fi
-
 # Don't build on tags because we'll already have built the commit.
 jobs:
   include: