Update playbooks_roles.rst

Fixes https://github.com/ansible/ansible/issues/7241
Removing hard coded link and replacing with reference
Add host to polling message

The message for when an async task has finished has the hostname in it. This adds it to the polling message as well:

```
<job 390794962174.18311> finished on 107.6.24.140
<job 390794962174.31779> finished on 69.90.50.171
<job 390794962174.12328> polling on 69.90.50.172, 6840s remaining
```
Update intro_installation.rst

Corrected casing of Jinja2 in pip dependencies.
Small python3 compat in vault to keep code in sync with v2
Merge the vault tempfile fix to the v2 tree
Updating v2 Role class code
Fixing up tests, removing some of the yaml error stuff from parsing

* moved old unittests for vault over to the new codebase
* reverted YAML error helpers and reverted the load() function
  in parsing/__init__.py, pending a rewrite of a new YAML loader
  class of some kind to encapsulate all of that
* fixed an error in in the module args parser regarding the shell/
  command argument parsing, where some additional arguments were
  being lost
Hook up the general parsing unittests and get them passing
Tell nose to include branches in its coverage reporting
Fix logic that prevents multiple action, local_action, and modules to be specified.
Adding in VaultEditor tests from old unittests
Merge pull request #9388 from mwarkentin/patch-2

Add host to polling message
Merge pull request #9394 from ronalexander/patch-1

Update intro_installation.rst
Use convert_bare instead of string formatting for raw vars in debug action plugin
Removing unnecessary import from v2 parsing init
Revert "remove complex_args_hack as it was only needed for Baby JSON"

This reverts commit a6029264b8194f0e6577d3e8cb4f853d779ef4f6.

Fixes #9400
Fix typo in vault edit helper code

Fixes #9399
Add AnsibleFest London link.
Fix the synopsis in ansible-pull man page.