clarify README instructions

Former-commit-id: b0db956e27fa35155260728774ebe5eb8c3368a3

README.md

@@ -16,12 +16,14 @@
 
 <ol>
 <li>Download and install Anaconda as described in <a href="https://docs.anaconda.com/anaconda/install/">https://docs.anaconda.com/anaconda/install</a></li>
-<li>Download the tool from <a href="https://github.rcac.purdue.edu/jprat/object-locator/archive/v1.3.1.zip">this link</a>, and decompress the zip.
+<li>Get the code from this git repository (or download the tool from <a href="https://github.rcac.purdue.edu/jprat/object-locator/archive/v1.3.1.zip">this link</a>, and decompress the zip).
+<li>(Optional) Check out a non-development version (such as `git checkout v1.3.1`).
 <li>Open the terminal in Linux/MacOS. In Windows, open the Anaconda Prompt.</li>
 <li>"cd" into the decompressed directory</li>
 <li>Download the trained models from <a href="https://lorenz.ecn.purdue.edu/~jprat/plant_locator/checkpoints">here</a> and put them in 
 <pre>object-locator-1.3.1/object-locator/checkpoints</pre>
 
+
 <li>Install the dependencies:</li>
 <pre>
 conda env create