Add unit tests for SoftLayer::Service#user_agent_header.
Add SoftLayer::Service#user_agent_header and sender User-Agent string with every request to SoftLayer API.
Bump version and note changes.
Update tests for changes from user_agent_header to user_agent.
Change user_agent_header to user_agent. Tighten up implementation.
Remove change history from lib/softlayer/base.rb.  Update CHANGELOG for 1.0.8.
Merge pull request #10 from cphrmky/useragent

Useragent