0.9.2

[97] AppVeyor builds shouldn't reset build ID when running tests (pvandervelde)
[201] Update readme (pvandervelde)
[254] All warnings and errors should have a code (pvandervelde)
[271] Document how to contribute to nBuildKit (pvandervelde)
[275] Make deployment of nBuildKit work (pvandervelde)
[280] deploy.pushto.gitbranch should create the repository directory before cloning (pvandervelde)
[281] GitCurrentBranch does not have a WorkingDirectory property (pvandervelde)
[282] Move Git, powershell, nuget base command line tasks into the core assembly (pvandervelde)
[284] Allow copying files from zip file (pvandervelde)
[285] Only load item groups if required for the current step (pvandervelde)
[286] GenerateTargetsFile task has assembly resolver that should also resolve MsBuild assemblies (pvandervelde)
[287] Copying files fails to copy to the correct directory hierarchy (pvandervelde)
[288] Allow downloading files from HTTP URL (pvandervelde)
[289] deploy.pushto.directory does not overwrite files (pvandervelde)
[290] Generated files should overwrite existing files (pvandervelde)