Update CONTRIBUTING.md

Added link to mailing list so that people can find it.
Merge branch 'stable'

* stable:
  (GH-426) Log Error output
  tests: add environment manipulation mocking facility
  helpers: add environment variable management abstractions
  rename Test-AdminRights to Test-ProcessAdminRights
  setup tests: fix formatting
  setup tests: do not vary by UAC status
  when running with administrative rights, set environment variables at Machine scope
  setup tests: with admin rights, variables should be set at Machine level regardless of UAC
  setup tests: add simulated standard user scenarios
  enable mocking Test-AdminRights for setup tests
  Test-AdminRights: request WindowsIdentity with minimal access necessary
  add Test-AdminRights helper
  setup tests: mock UAC status
  setup tests: conditionally test default installation
  add tests for Chocolatey setup (Initialize-Chocolatey)
  tests: add environment variable handling facilities
  (maint) formatting
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Update CONTRIBUTING.md
Merge branch 'stable'

* stable:
  (GH-493) First set of specs for update
  v0.9.8.24-rc1
  (GH-493) Cleanup Chocolatey-Update
  (GH-379) Upgrade Nuget.exe to 2.8.2
  (infra) deprecation message for installmissing
  (maint) formatting
  (maint) hide folder creation from output
Merge branch 'stable'

* stable:
  (GH-499) Do not throw if missing chocolateyUninstall.ps1
  (maint) formatting
Merge branch 'stable'

* stable:
  0.9.8.24-rc2
  (maint) be sure RD software is included in copyright notices
  (GH-494) Issue new default install location deprecation warning
Merge branch 'stable'

* stable:
  (doc) Changelog / nuspec updates for 0.9.8.24 final
Merge branch 'stable'

* stable:
  v0.9.8.24
  (doc) chocolatey.org now parses markdown, so let's do that
  (doc) fix up releasenotes
Merge branch 'stable'
Merge branch 'stable'

* stable:
  (GH-505) if using elevation, don't minimize the window
  (GH-505) handle user canceled elevation
  v0.9.8.25
  (doc) update changelog/nuspec
  (GH-505) Fix elevation required causes bug
  (doc) update proprietary license for shimgen.exe
Merge branch 'stable'

* stable:
  (doc) fixed a missed word in shimgen licensing
  (maint) formatting
  (doc) do not give the impression that an actual virus scan is happening
  (GH-510) Chocolatey should find tools in it's default install location
Merge branch 'stable'

* stable:
  (GH-508)(GH-509) shimgen fix/improvements
Merge branch 'stable'

* stable:
  v0.9.8.26-alpha1
  (doc) update changelog / nuspec
Merge branch 'stable'

* stable:
  (GH-507) Fix - Update chocolatey's shims
Merge branch 'stable'

* stable:
  (GH-256) cpack/cpush always return 0 exit code even w/errors
  (maint) formatting
  (GH-516) Guard all Wait-Process if posh v3+
  Fix bogus error message with error code from 7za amiss
  (GH-514) Fix setting errored during install
Merge branch 'stable'

* stable:
  (GH-509) Shimgen-waitforexit
Merge branch 'stable'

* stable:
  v0.9.8.26
  (doc) update changelog/nuspec
  (GH-519) Issue warning if process doesn't have admin token
  v0.9.8.26-alpha2
Merge branch 'stable'

* stable:
  v0.9.8.27-beta1
  (doc) update changelog / nuspec
  (maint) Debug should capture operating system information
  (GH-516) If process has not yet exited, wait the process
Merge branch 'stable'

* stable:
  v0.9.8.27
  (build) update location of chocolatey in build

Conflicts:
	build.proj
(GH-525) adding gittip shield