Update change log and version for release v0.1.8

CHANGELOG.md

+# v0.1.8
+* Add support for Chef 10 (#3)
+* Properly update `resource_collection` when unshifting (#4)
+  * Thanks @mpasternacki
+
 # v0.1.6
 * Fix version number
 

metadata.rb

 name 'dpkg_autostart'
-version '0.1.7'
+version '0.1.8'
 maintainer 'Chris Roberts'
 maintainer_email 'chrisroberts.code@gmail.com'
 description 'Control service actions initialized from dpkg'