Implement input handling in Env
Implement Action#input, delegating to env input
Implement `ask' recipe keyword
Allow `ask' action to customize choices prompt
Bump version to 0.1.11
Remove feature exposing env object in recipe DSL
Implement Remote::FS#dir?
Implement `has_dir' condition keyword
Fix some indentation in FileWriter spec
Implement `mkdir' task action
Bump version to 0.1.12
Implement a key/value registry at env level
Implement `set' and `get' recipe keywords:

  `set' registers a value at given index in env registry, `get'
retrieves a value at given index.
Implement `get' task keyword, fetch from registry
Refactor forwardable require calls
Fix Remote::FS#file_write spec:

* Fix file double name;
* Remove uneeded .as_null_object calls on doubles.
Implement Remote::FS#file_read
Implement `file_contains' condition keyword
Remove extra empty line in specs