Release v0.9.0

Change dist to trusty to fix travis pipeline

https://travis-ci.community/t/error-installing-oraclejdk8-expected-feature-release-number-in-range-of-9-to-14-but-got-8/3766/5

Release v0.8.1

• PR #42: Updated assertJ to v3.9.1
• PR #43: Fixed problem with validation of enum values
• PR #44: Enabled configuration for loosely match responses
• PR #45: Enhanced definition validation
• PR #46: Avoid NPE if Definition does not contain properties
• PR #47: Schema resolver avoid NPE
• PR #48: Check definition instance before validating required properties
• PR #49: Added validation for enums

Release v0.8.0

• PR #35: Added new isEqualTo with auth for secured endpoints

• PR #36: Added missing validation message for property types

• PR #37: Added basePath to paths if no path prefix is configured