Merge branch 'release/3.0.0' into develop
Create 'services' parameter to snmp class

All the work was done for this already, in the $snmp::params class.  It was even already documented, but just not in the parameter list.

Signed-off-by: Michael Arnold <github@razorsedge.org>
Add contribution instructions to README.md.
Convert fixtures repositories to use https.
Expand Puppet versions tested in Travis-CI.
Merge branch 'develop' of github.com:razorsedge/puppet-snmp