Set package README, license expression, and development dependency (#41)

* Upgrade package license to expression

Using an expression for the well-known BSD-3 Clause license instead of a
URL (which makes it look like the package is using a custom license) and simplifes
compliance for users.

* Add package readme

* Mark package as a development dependency

Source/Moq.Analyzers.Test/PackageTests.Baseline#contents.verified.txt

@@ -1,5 +1,6 @@
 /
 |-- Moq.Analyzers.nuspec
+|-- README.md
 |-- analyzers
 |   |-- dotnet
 |   |   |-- cs

Source/Moq.Analyzers.Test/PackageTests.Baseline#manifest.verified.nuspec

@@ -3,7 +3,10 @@
     <id>Moq.Analyzers</id>
     <version>********</version>
     <authors>Andrey "Litee" Lipatkin</authors>
-    <licenseUrl>https://github.com/Litee/moq.analyzers/blob/master/LICENSE</licenseUrl>
+    <developmentDependency>true</developmentDependency>
+    <license type="expression">BSD-3-Clause</license>
+    <licenseUrl>https://licenses.nuget.org/BSD-3-Clause</licenseUrl>
+    <readme>README.md</readme>
     <projectUrl>https://github.com/Litee/moq.analyzers</projectUrl>
     <description>Roslyn analyzer that helps to write unit tests using Moq mocking library by highlighting typical errors and suggesting quick fixes. Port of Resharper extension to Roslyn. Find the full list of detected issues at project GitHub page.</description>
     <releaseNotes>Upgraded to support Visual Studio 2019</releaseNotes>

Source/Moq.Analyzers/Moq.Analyzers.csproj

@@ -31,13 +31,15 @@
   <PropertyGroup>
     <PackageId>Moq.Analyzers</PackageId>
     <Authors>Andrey "Litee" Lipatkin</Authors>
-    <PackageLicenseUrl>https://github.com/Litee/moq.analyzers/blob/master/LICENSE</PackageLicenseUrl>
+    <PackageLicenseExpression>BSD-3-Clause</PackageLicenseExpression>
     <PackageProjectUrl>https://github.com/Litee/moq.analyzers</PackageProjectUrl>
     <PackageRequireLicenseAcceptance>false</PackageRequireLicenseAcceptance>
+    <PackageReadmeFile>README.md</PackageReadmeFile>
     <Description>Roslyn analyzer that helps to write unit tests using Moq mocking library by highlighting typical errors and suggesting quick fixes. Port of Resharper extension to Roslyn. Find the full list of detected issues at project GitHub page.</Description>
     <PackageReleaseNotes>Upgraded to support Visual Studio 2019</PackageReleaseNotes>
     <Copyright>2015-2019 Andrey Lipatkin</Copyright>
     <PackageTags>moq, mock, test, analyzers</PackageTags>
+    <DevelopmentDependency>true</DevelopmentDependency> 
     <NoPackageAnalysis>true</NoPackageAnalysis>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
   </PropertyGroup>
@@ -62,6 +64,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <None Include="$(RepoRoot)\README.md" Pack="true" PackagePath="/"/>
     <None Update="tools\*.ps1" CopyToOutputDirectory="Always" Pack="true" PackagePath="" />
     <None Include="$(OutputPath)\$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
   </ItemGroup>