Bump version to 0.6.4

CHANGELOG.md

 # Change Log
 
-## [Unreleased]
+## [0.6.4] - 2018-03-21
 
 ### Added
 
@@ -157,7 +157,8 @@ Initial release
 
 
 
-[Unreleased]: https://github.com/sdispater/poetry/compare/0.6.3...master
+[Unreleased]: https://github.com/sdispater/poetry/compare/0.6.4...master
+[0.6.4]: https://github.com/sdispater/poetry/releases/tag/0.6.4
 [0.6.3]: https://github.com/sdispater/poetry/releases/tag/0.6.3
 [0.6.2]: https://github.com/sdispater/poetry/releases/tag/0.6.2
 [0.6.1]: https://github.com/sdispater/poetry/releases/tag/0.6.1

poetry/__version__.py

-__version__ = '0.6.4-beta.1'
+__version__ = '0.6.4'

pyproject.toml

 [tool.poetry]
 name = "poetry"
-version = "0.6.4-beta.1"
+version = "0.6.4"
 description = "Python dependency management and packaging made easy."
 authors = [
     "Sébastien Eustace <sebastien@eustace.io>"