Revert "Clarify backwards compatibility for major version 0"

This reverts commit 0f25f18, opencontainers#253.
Now that we're on to 1.0, we don't need to talk about 0.x.  And the
lack of 0.x backwards compatability is covered by SemVer 2.0 section 4
[1]:

  Major version zero (0.y.z) is for initial development.  Anything may
  change at any time.  The public API should not be considered stable.

so removing the echo from our spec doesn't actually change anything.

The conflict is due to 4e63ee0 (config: qualify the name of the
version field, 2016-01-13, opencontainers#309), and only impacted the context and
line-wrapping around the sentence I'm removing.

Conflicts:
	config.md

[1]: http://semver.org/spec/v2.0.0.html

Signed-off-by: W. Trevor King <wking@tremily.us>

config.md

@@ -13,7 +13,6 @@ Below is a detailed description of each field defined in the configuration forma
 * **`ociVersion`** (string, required) MUST be in [SemVer v2.0.0](http://semver.org/spec/v2.0.0.html) format and specifies the version of the OpenContainer specification with which the bundle complies.
 The OpenContainer spec follows semantic versioning and retains forward and backward compatibility within major versions.
 For example, if an implementation is compliant with version 1.0.1 of the spec, it is compatible with the complete 1.x series.
-NOTE that there is no guarantee for forward or backward compatibility for version 0.x.
 
 ### Example