Add Parallel Bundle Install as ruby til.

README.md

@@ -14,6 +14,7 @@ I shamelessly stole this idea from
 ## ruby
 
 - [Limit Split](ruby/limit-split.md)
+- [Parallel Bundle Install](ruby/parallel-bundle-install.md)
 - [Summing Collections](ruby/summing-collections.md)
 
 ## vim

ruby/parallel-bundle-install.md

@@ -0,0 +1,13 @@
+# Parallel Bundle Install
+
+The `bundle install` command can take quite a while sometimes. This is
+especially true for when you are setting up a fresh dev environment for an
+existing project. Fortunately, Bundler provides a flag for parallelizing
+the gem installs and Bundler is smart enough that it knows how to resolve
+the dependencies so that this is possible in the first place. Just tell
+Bundler how many concurrent jobs you want it to install with (4 is a good
+number) and let it do the rest of the work.
+
+```bash
+$ bundle install --jobs 4
+```