Update the install pages (both TF site and GitHub) to require a TF version of 1.15 or higher.

PiperOrigin-RevId: 268156703

Author: DualityGap

README.md

@@ -36,12 +36,17 @@ to NSL.
 
 ## Getting started
 
-Install the prebuilt pip package using
+You can install the prebuilt NSL pip package by running:
 
 ```bash
 pip install neural-structured-learning
 ```
 
+For more detailed instructions on how to install NSL as a package or to build it
+from source in various environments, please see the [installation guide](g3doc/install.md)
+
+Note that NSL requires a TensorFlow version of 1.15 or higher.
+
 ## Contributing to NSL
 
 Contributions are welcome and highly appreciated - there are several ways to

g3doc/install.md

@@ -12,6 +12,8 @@ Learning (NSL) in TensorFlow:
 *   If you have a unique machine configuration,
     [build NSL](#build-the-neural-structured-learning-pip-package) from source.
 
+Note: NSL requires a TensorFlow version of 1.15 or higher.
+
 ## Install Neural Structured Learning using pip
 
 #### 1. Install the Python development environment.
@@ -46,8 +48,6 @@ Note: To exit the virtual environment, run `deactivate`.
 
 #### 3. Install TensorFlow
 
-Neural Structured Learning requires TensorFlow 1.15 or higher.
-
 CPU support:
 
 <pre class="prettyprint lang-bsh">