website: Standardize GitHub capitalization

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
website,util/packer: Standardize VirtualBox capitalization

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
website,CONTRIBUTING: Unify contributing content

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
website: Capitalize Docker

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
website: Capitalize Go

Signed-off-by: Jonathan Rudenberg <jonathan@titanous.com>
Merge pull request #312 from flynn/capitalization

Capitalization cleanup