Adds Connection Services / Post Requests / Fixes get customer

[arvel]

This adds PortfolioManager connection services to the gem starting with listing connection requests and accepting/rejecting them. This required adding post requests: https://portfoliomanager.energystar.gov/webservices/home/api/connection

Also fixes type in get customer and adds associated spec.

[coveralls]

Coverage remained the same at 100.0% when pulling b310aa1 on arvel:master into f691fa2 on mejackreed:master.

[mejackreed]

Thanks for the contribution!

[arvel]

@mejackreed Thanks for the merge!