get_version method returns HTTP 403

[Puneeth]

The get_version() method doesn't seem to work and raises a HTTPError exception.

how to reproduce this bug:

````
import jenkins

server = jenkins.Jenkins('https://jenkins.my-org.com', username='Puneeth-n', password='12345')

print server.get_version()
````

Solution:
Add authentication to HTTP headers.

I have submitted the code for review at master/fix/get_version

[Lil (lil2006)]

i have a bit different error on jenkins 2.1. Error communications with server

[Khai Do (zaro0508)]

@Puneeth, I assume you mean this change https://review.openstack.org/#/c/305882

if so the tests are failing for it so would you mind fixing up the tests?

[OpenStack Infra (hudson-openstack)]

Change abandoned by Sorin Sbarnea (<email address hidden>) on branch: master
Review: https://review.openstack.org/305882
Reason: This would have to be rewritten (if still needed) as we switched to use of requests library.

[Gregory Shklover (gshklover)]

Suggested fix:

    def get_version(self):
        response = self._session.get(self._build_url(''))
        return response.headers['X-Jenkins']

[J D (jdearte)]

This is still an issue with version 1.8.2

Interesting thing

If follow Example 1 - it works!

```
import jenkins

server = jenkins.Jenkins('http://localhost:8080', username='myuser', password='mypassword')
user = server.get_whoami()
version = server.get_version()
print('Hello %s from Jenkins %s' % (user['fullName'], version))
```

If I change the order of the calls (get_version before get_whoami), it will FAIL with 403

If I alter it to only call get_version, it will FAIL with 403