Update next_steps.md

next_steps.md

@@ -11,7 +11,15 @@ Git and github are extremely powerful systems and there is a lot more you can le
 
 **Testing and version control**
 
-By employing testing, you can ensure that your code behaves the way you expect
+By employing testing, you can ensure that your code behaves the way you expect.
 
 * Unit testing in R, the bare minimum - http://www.johnmyleswhite.com/notebook/2010/08/17/unit-testing-in-r-the-bare-minimum/
-* Continuous Integration. Every time you push a change, your tests are automatically run. - https://docs.travis-ci.com/user/languages/r
+* Continuous Integration. Every time you push a change to github, your tests are automatically run. - https://docs.travis-ci.com/user/languages/r
+
+**Dealing with dependencies**
+
+Your code works on your machine but not on someone else's because they are using a different version of R and have different versions of packages installed. How might be fix this?
+
+* https://rstudio.github.io/packrat/ - Packrat enhances your project directory by storing your package dependencies inside it.
+* https://mran.microsoft.com/ - MRAN, The 'Managed CRAN' has snapshots of every package going back to 2014
+