docs: Specify Python versions using double pipe (#1397)

* Fix specification of Python versions for dependencies using double
  pipe (`||`) instead of using an array which leads to confusion (see for
  instance https://github.com/sdispater/poetry/issues/847).

* Fixes #847

Signed-off-by: mr.Shu <mr@shu.io>

docs/docs/versions.md

@@ -126,7 +126,7 @@ pathlib2 = { version = "^2.2", python = "~2.7" }
 
 ```toml
 [tool.poetry.dependencies]
-pathlib2 = { version = "^2.2", python = ["~2.7", "^3.2"] }
+pathlib2 = { version = "^2.2", python = "~2.7 || ^3.2" }
 ```