Merge pull request #59 from dazaris/master

Fix to CampaignFilter class. Optional flag 'uses_segment' was non-nullabable bool
Reinstate MergeVar for explicit specification of lists/subscribe merge_vars param

Fixes #61

Re-instatement of the deleted MergeVar class for utilization on the Lists.Subscribe method.  Reasoning:

 - people who just want to use the API should have the most common fields available to them in this class... it also "self-documents" the lists/subscribe function, and makes it ready to use out of the box.

 - Interests/Groups are the recommended way to deal with multiple subscriber interests / mailings: http://kb.mailchimp.com/article/best-practices-for-lists#manage ("Maintain a single list per client or organization in your account.")  So utilizing at least the grouping parameters is (or should be) very commonplace.

 - Assuming you re-instate the MergeVar class, here is an approach that works for adding additional fields to the merge_vars parameter:

 1) When you create your arguments object, cast the MergeVar type as an object so it properly gets serialized in the MailChimpManager.Subscribe:

```C#
            //  Create our arguments object:
            object args = new
            {
                apikey = this.APIKey,
                //...
                merge_vars = (object)mergeVars,
                // cast to object so ServiceStack grabs the entire object
                // (IE if it is inherited with custom merge fields added),
                // not just the base type
                //...
            };
```

 2) Then simply inherit the object and add the fields needed:

```C#
        [System.Runtime.Serialization.DataContract]
        public class MyMergeVar : MergeVar
        {
            [System.Runtime.Serialization.DataMember(Name = "FNAME")]
            public string FirstName
            {
                get;
                set;
            }
            [System.Runtime.Serialization.DataMember(Name = "LNAME")]
            public string LastName
            {
                get;
                set;
            }
        }
```

 3) Then just pass an instance of your inherited class to Subscribe.
Merge pull request #62 from AndrewKoransky/master

Reinstate MergeVar for explicit specification of lists/subscribe merge_vars param
correct / add docs for subscribe with merge vars
Merge pull request #63 from AndrewKoransky/master

correct / add docs for subscribe with merge vars
Updated README

Reformatted code examples to have easier-to-read formatting
Updated README

Even more fancy formatting
WaitTime & WaitUnits data attributes wrong way round
Added support to inline-css method.
Merge pull request #67 from paulandrewcampbell/patch-1

WaitTime & WaitUnits data attributes wrong way round
Merge pull request #68 from rafaelbac/master

Added support to inline-css method.
Updated NuGet package spec
Adds support for updating a member
Changed type of mergeVars parameter of Subscrube to support not only successors of MergeVar but custom dictionary too(Dictionary<string, string>).
Added campaigns/template-content support
wrong type of the Sections property
Merge pull request #71 from Soda-Digital/update-member-support

For Review: Adds support for updating a member
implemented reports/bounce-messages, reports/opened, reports/unsubscribes
Convert to .NET 3.5

Converts target framework to .NET 3.5, with minor code changes to
support conversion.
Merge pull request #73 from Yagg/master

campaigns/template-content support and small changes to Subscribe method