whitespace fixes
Use 'cd' in vendor_gems as a block

The 'cd' call in vendor_gems.rake doesn't return up to its previous location
afterwards, because its not in a do..end block. This means the tarball ends up
in vendor/cache/ instead of pkg/. This commit updates the task accordingly.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Merge pull request #134 from MosesMendoza/maint/master/fix_vendor_gems_cd

Maint/master/fix vendor gems cd