Update stormpath to version 0.18.0 🚀

[greenkeeperio-bot]

Hello 👋

🚀🚀🚀

stormpath just published its new version 0.18.0, which is not covered by your current version range.

If this pull request passes your tests you can publish your software with the latest version of stormpath – otherwise use this branch to work on adaptions and fixes.

Happy fixing and merging 🌴

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The new version differs by 18 commits .

• 0dd5a0e Merge pull request #411 from stormpath/release-0.18.0
• dfb779b Merge pull request #412 from stormpath/greenkeeper-grunt-contrib-watch-1.0.0
• b9c58bd chore(package): update grunt-contrib-watch to version 1.0.0
• d2f80c4 Release 0.18.0
• 1a0bb41 Merge pull request #409 from stormpath/jwt-authenticator-for-password-grant
• 039eaed JwtAuthenticator can process client_credentials tokens
• 7643752 Merge pull request #407 from stormpath/feature-add-ability-to-invalidate-cache
• 0c0341f add tests for InstanceResource.invalidate()
• 4e316ad rename invalidateCache to just invalidate
• 566d4e5 add the ability to invalidate the cache of an InstanceResource
• 5d6ddb6 Merge pull request #405 from stormpath/fix-omitted-account-save-error
• 033e118 Merge pull request #406 from stormpath/greenkeeper-moment-2.12.0
• c8d72d3 chore(package): update moment to version 2.12.0
• 7ed598b add test to assert that Account.save() can throw errors
• fc3b086 Merge pull request #400 from stormpath/greenkeeper-load-grunt-tasks-3.4.1

There are 18 commits in total. See the full diff.

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