Release 0.5.1
Merge branch 'master' of github.com:bkeepers/dotenv

* 'master' of github.com:bkeepers/dotenv:
  more explicitness of where the file is
  Seems to read better when being explicit.
  Correction: Don't allow for caps 'EXPORT' command
  Allow for env variables set with 'export' keyword
  Test env file with 'export ' before variables
  Allow double quotes in .env variable assignment