Reduced API calls significantly

[boostchicken]

Using the ASG tag on EC2 instances instead of enumerating them by the ASG API

[pleshakov]

@boostchicken thanks for the PR. we'll test your changes in the next few days.

[pleshakov]

@boostchicken
Your changes look good! Thanks again

Before we merge, could you fix a few things:

• run the modified source files through go fmt tool to fix formatting
• fix the spelling of the resverations variable
• change the version back to 0.1-2. We'll prepare a new release with 0.2-1 later this spring and release the new packages as well. your changes will go into that release.
• squash all the commits into a single one
• I think this method getInstancesOfReservations becomes redundant. Could you possibly remove it and move the code into GetPrivateIPsOfInstancesOfAutoscalingGroup

[Rulox]

This was addressed in #29

Closing, thanks.