message: Update guide.md
  Fixing grammatical errors in the Installation instructions
diff: @@ -24,9 +24,9 @@ Installation instructions at https://www.tensorflow.org/install/
  The contents of this guide are compatible with TensorFlow 1.5.
  However, if you run into bugs that are fixed in source but not the
  -release, you may want to either either [building from
  +release, you may want to either [build from
  source](https://www.tensorflow.org/install/install_sources)
  -or the try latest nightly builds. The nightly builds are available as:
  +or try a nightly build. The nightly builds are available as:
  - [`pip` packages](https://github.com/tensorflow/tensorflow/blob/master/README.md#installation) and
  