Escape env values rather than simply quote them.

[mheath]

This implements a fix for #144.

[cfdreddbot]

Hey mheath!

Thanks for submitting this pull request! I'm here to inform the recipients of the pull request that you've already signed the CLA.

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this. You can view the current status of your issue at: https://www.pivotaltracker.com/story/show/79406518.

[emalm]

Hi, @mheath,

Thanks for the PR. We are concerned about this change potentially altering behavior around expansion of the user-provided environment variables. The WIP commit 9dfa3c3 does limit the escaping to only the system-provided variables, so it seems like it would address your problems with the evaluation of the VCAP_SERVICES credential values. You'd be welcome to submit a new PR by adding (a potentially a small amount of) changes to the work that @julz and @fraenkel started in that branch.

Best,
@ematpl && @stupakov, for the CF Runtime team

[crhino]

Closing this as the issue has been fixed in commit above.