Update release info
Merge pull request #1541 from ogail/ver

Update release info
update changelog for 0.6.15
add Stop-AzureVM change
update readme
Merge branch 'release' of https://github.com/WindowsAzure/azure-sdk-tools into release
Merge pull request #1556 from guangyang/release

changelog and readme for 0.6.15
Merge pull request #1576 from WindowsAzure/release

Release 0.6.15
Merge pull request #1577 from WindowsAzure/master

Merge master into dev