object: remove extra table close tag
object: collect all headers in a single variable

This makes it easier to reset the state.
swift: add postObject method
swiftSpec: add more detailed postObject tests
object: allow metadata to be edited (fixes #23)
object: allow removing headers
swift-sim: add support for headObject

Despite what the docs say, support for whenHEAD was added later,
probably in version 1.3.0.
e2e/swift: test status values headObject
e2e/swift: generalize callHeadObject to callSwiftMethod

This will help us simplifying the other tests.
e2e/swift: use callSwiftMethod in listObject tests
e2e/swift: use callSwiftMethod in deleteObject tests
e2e/swift: manually serialize executeAsyncScript args (fixes #103)
e2e: add test for showing object metadata
e2e: extract useful helper functions in metadata test
swift-sim: add support for postObject
e2e: test editing metadata
Merge pull request #104 from mgeisler/editable-metadata

Editable metadata