Add pipfile to supported Python PIP formats (#4302)

See https://github.com/zendesk/pakkr/network/dependencies for an example of a pipfile in the dependency graph.

Author: juxtin

content/github/visualizing-repository-data-with-graphs/about-the-dependency-graph.md

@@ -70,7 +70,7 @@ The recommended formats explicitly define which versions are used for all direct
 | `dotnet` CLI | .NET languages (C#, C++, F#, VB)  |   `.csproj`, `.vbproj`, `.nuspec`, `.vcxproj`, `.fsproj` |  `.csproj`, `.vbproj`, `.nuspec`, `.vcxproj`, `.fsproj`, `packages.config` |
 | Maven | Java, Scala |  `pom.xml`  | `pom.xml`  |
 | npm | JavaScript |            `package-lock.json` | `package-lock.json`, `package.json`|
-| Python PIP      | Python                    | `requirements.txt`, `pipfile.lock` | `requirements.txt`, `pipfile.lock`, `setup.py`* |
+| Python PIP      | Python                    | `requirements.txt`, `pipfile.lock` | `requirements.txt`, `pipfile`, `pipfile.lock`, `setup.py`* |
 | RubyGems             | Ruby           | `Gemfile.lock` | `Gemfile.lock`, `Gemfile`, `*.gemspec` |
 | Yarn | JavaScript | `yarn.lock` | `package.json`, `yarn.lock` |