Bump version to 5.6.0 (#190)

Author: rogebrd

buildall.ps1

@@ -19,7 +19,7 @@ $nugetPath = "$nugetDir\nuget.exe"
 $nugetSpecPath = "$sourceDir\Dropbox.Api.nuspec"
 $docBuildPath = Resolve-Path "doc\StoneDocs.shfbproj"
 $majorVersion = "5.0"
-$releaseVersion = "5.5.0"
+$releaseVersion = "5.6.0"
 $assemblyInfoPath = "$sourceDir\AppProperties\AssemblyInfo.cs"
 $signKeyPath = "$sourceDir\dropbox_api_key.snk"
 $releaseNotes = @'

dropbox-sdk-dotnet/Dropbox.Api/Dropbox.Api.nuspec

@@ -2,7 +2,7 @@
 <package>
   <metadata>
     <id>Dropbox.Api</id>
-    <version>5.5.0</version>
+    <version>5.6.0</version>
     <title>Dropbox v2 API</title>
     <authors>Dropbox</authors>
     <owners>Dropbox</owners>