Remove nlog.config dependency from nuget specification.

The nlog.config dependency was introduced by mistake. Removing
to clean up the nuget package.
Merge pull request #18 from DonMcNamara/removenlogconfig

Remove nlog.config dependency from nuget specification.
Downgraded Nlog to 2.0
Building for both .NET 2.0 and .NET 4.0

- Nuspec file packages up both
- Psake build calls MSBuild twice - once per framework
- Ensure clean is called before each build to prevent framework
fist fights
Merge pull request #17 from LinkExe/net20

Downgraded NLog.AirBrake to use .Net 2.0
Attempt to fix build server with an additional trailing \ on MSBuild OutDir
Merge pull request #19 from LinkExe/buildfix-outdir

Attempt to fix build server with an additional trailing \ on MSBuild Out...
Attempt to remove ; from build errors
Merge pull request #20 from LinkExe/buildfix-outdir

Attempt to remove ; from build errors
Conditionally include Extensions.cs only on .NET 2

Compiler warning CS1685 is emitted on .NET 4 when redefining
System.Runtime.CompilerSerices.ExtensionAttribute

This should not compile this code for the .NET 4 release
A missing " will get you every time!
Must include System.Core in .NET 4.0

To pick up ExtensionAttribute in .NET 3.5 and .NET 4.0, we have
to include System.Core.

Note that in .NET 4.5, this attribute is in mscorlib
NLog version is based on TargetFrameworkVersion

More MSBuild hackery
Change where our NLog reference is coming from, when
building against different framework versions
Should allow us to use Error() rather than ErrorException()
Merge pull request #25 from Elindalyne/issue-23

Fixing Issue 23. This should allow you to use error or errorexception
Should fix build
Merge pull request #26 from Elindalyne/issue-23

Should fix build
Fixing Build - moved LogEvent extensions into its own file
Merge pull request #27 from Elindalyne/issue-23

Fixing build -  moved Logevent extensions to its own file
Environment Variable Addition
-When logging with LogEventInfo, you can now set properties on the
LogEventInfo and they will display on the Environment Tab on Errbit.