Creating Contacts in Outlook [Started development]

Hi guys,

Since this library had some amazing implementations and did a lot of the things I needed I decided to expand it and put some effort in to it.
I'm not used to anything related Exchange / SOAP but tried to manage with what was already here.
I've forked this repository and added as much as I could for now. You can see my added code here: https://github.com/linkedin/pyexchange/compare/master...Yenthe666:master

I've now ran stuck on the following error:

```
pyexchange.exceptions.FailedExchangeException: Unable to connect to Exchange: 500 Server Error: Internal Server Error
```

Which comes from exceptions.py in the function FailedExchangeException:

```
class FailedExchangeException(Exception):
"""Raised when the Microsoft Exchange Server returns an error via SOAP for a request."""
pass
```

Example code to create a new contact:

```
from pyexchange import Exchange2010Service, ExchangeNTLMAuthConnection

URL = u'https://mail.yourdomain.com/EWS/Exchange.asmx'
USERNAME = u'DOMAIN\\yenthe'
PASSWORD = u"mypassword"
from datetime import datetime
from pytz import timezone

# Set up the connection to Exchange
connection = ExchangeNTLMAuthConnection(url=URL,
username=USERNAME,
password=PASSWORD)

service = Exchange2010Service(connection)

# You can set event properties when you instantiate the event...
contact = service.contact().new_contact(
name=u"Yenthe",
company_name = u"Google",
)

# Connect to Exchange and create the event
contact.create()
```

Could anybody help me and finish this implementation? I do not know how to fix this issue but I think this is a good start.

Review the linked fork comparison and the existing contact implementation, then trace contact.create() through the Exchange2010Service and the request handling in exceptions.py. Reproduce the 500 error with the provided example and compare the generated SOAP request with the existing Exchange operations. Done means contact creation works without FailedExchangeException.

Written by the indexing model from the issue text.