message: Update changelog for 1.12.1
diff: * There currently is no completion support for package references in csproj files. ([#1156](https://github.com/OmniSharp/omnisharp-vscode/issues/1156))
  +## 1.12.1 (August 14, 2017)
  +
  +* MSBuild support properly sets CscToolExe to 'csc.exe' to address issues when a project's MSBuild targets have set it to 'mcs.exe'. ([#1707](https://github.com/OmniSharp/omnisharp-vscode/issues/1707))
  +
  ## 1.12.0 (August 8, 2017)
  #### Debugger
  