semantic-release: Fail builds on error

If no NPM token is set and semantic-release is run as script in Travis, the build still passes and semantic-release exits with 0.

1.81s$ npm run semantic-release


> iterare@1.0.0 semantic-release /home/travis/build/felixfbecker/iterare

> semantic-release


[Semantic release]: Load plugin verifyConditions from @semantic-release/npm

[Semantic release]: Load plugin verifyConditions from @semantic-release/github

[Semantic release]: Load plugin verifyConditions from @semantic-release/condition-travis

[Semantic release]: Load plugin getLastRelease from @semantic-release/npm

[Semantic release]: Load plugin analyzeCommits from @semantic-release/commit-analyzer

[Semantic release]: Load plugin generateNotes from @semantic-release/release-notes-generator

[Semantic release]: Load plugin publish from @semantic-release/npm

[Semantic release]: Load plugin publish from @semantic-release/github

[Semantic release]: Run automated release from branch master

[Semantic release]: Call plugin verify-conditions

[Semantic release]: Verify authentication for registry https://registry.npmjs.org/

[Semantic release]: ENONPMTOKEN No npm token specified.



The command "npm run semantic-release" exited with 0.