Pin dotnet-nightly package on Travis

.travis.yml

@@ -9,7 +9,7 @@ before_install:
   - sudo sh -c 'echo "deb [arch=amd64] http://apt-mo.trafficmanager.net/repos/dotnet/ trusty main" > /etc/apt/sources.list.d/dotnetdev.list'
   - sudo apt-key adv --keyserver apt-mo.trafficmanager.net --recv-keys 417A0893
   - sudo apt-get -qq update
-  - sudo apt-get install -y dotnet-nightly
+  - sudo apt-get install -y dotnet-nightly=1.0.1.001252-1
 script:
   - dotnet restore
   - ./build.sh

README.md

@@ -55,9 +55,10 @@ git submodule update --init --recursive -- src/monad src/windows-build test/Pest
 
 We use the [.NET Command Line Interface][dotnet-cli] (`dotnet-cli`) to build
 the managed components, and [CMake][] to build the native components (on
-non-Windows platforms). Install `dotnet-cli` by following their [documentation][]
-(make sure to install the `dotnet-nightly` package on Linux to get the latest
-version).
+non-Windows platforms). Install `dotnet-cli` by following their [documentation][].
+
+**Make sure to `apt-get install dotnet-nightly=1.0.1.001252-1` for a known,
+good version.**
 
 > Note that OS X dependency installation instructions are not yet documented,
 > and Core PowerShell on Windows only needs `dotnet-cli`.