Forbid addVariable and addProperty to global namespace (vinniefalco#167)

* Forbid addVariable for global namespace.
* Forbid addProperty for global namespace.
* Add Namespace unit tests.
* Fix compilation error.

Merge pull request vinniefalco#68 from toski/master

Issue vinniefalco#66 fixed

Merge branch 'release'

HOTFIX: Remove spurious semicolon from namespace declaration

Merge branch 'develop'

Same as 0.2.2

Update README

update CHANGES for 0.2.1 release

Version 0.2

Version 0.1