nosudo on CentOS and Fetch Changelogs on Amazon, RHEL (#448)

* Use repoquery for no sudo and avoid unintended line feed of yum or rpm. #444

* Change data type of enablerepo in config.toml. string to array

* Fetch yum changelogs at once then grep CVE-IDs

* Fix changelog parse logic and Update Gopkg

.travis.yml

@@ -1,6 +1,5 @@
 language: go
 
 go:
-  - 1.7
   - 1.8