Ansible 2.3 support

- Fix when clauses in various places
- Update requirements.txt
- Fix README.md

Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>

requirements.txt

@@ -1,14 +1,3 @@
-ansible==2.2.1.0
+ansible>=2.3.0
 netaddr
-# Ansible 2.2.1 requires jinja2<2.9, see <https://github.com/ansible/ansible/blob/v2.2.1.0-1/setup.py#L25>,
-# but without explicit limiting upper jinja2 version here pip ignores
-# Ansible requirements and installs latest available jinja2
-# (pip is not very smart here), which is incompatible with with
-# Ansible 2.2.1.
-# With incompatible jinja2 version "ansible-vault create" (and probably other parts)
-# fails with:
-#   ERROR! Unexpected Exception: The 'jinja2<2.9' distribution was not found 
-#   and is required by ansible
-# This upper limit should be removed in 2.2.2 release, see:
-# <https://github.com/ansible/ansible/commit/978311bf3f91dae5806ab72b665b0937adce38ad>
-jinja2>=2.8,<2.9
+jinja2>=2.9.6