Align summary values in text email template

Aligning these values in the text email template will make it a little
easier to scan and a little more aesthetically pleasing.

Before example:

  Deployer: John Doe
  Application: Application
  Branch: master
  Environment: test
  Time: 01/09/2014 at 03:44 PM PDT

After example:

  Deployer:     John Doe
  Application:  Application
  Branch:       master
  Environment:  test
  Time:         01/09/2014 at 03:44 PM PDT
Merge pull request #71 from lencioni/text-email

Align summary values in text email template