Fix OS Arch chech

Fixed check helps when you need to deploy 64-bit zabbix-agent from
32-bit cmd.exe process. It's needed when you use tools like puppet and
chocolatey package provider for puppet which uses 32-bit Ruby and so
32-bit cmd.exe. Current check returns false when running under 32-bit cmd.exe
Version upgrade

Upgraded zabbix agent to 2.0.8 as well as nuspec version
Merge branch 'master' of https://github.com/applewiskey/zabbix-agent-chocolatey
Merge branch 'ver-upgrade'

Conflicts:
	zabbix-agent.nuspec