Add support for upgrading to 2.6 (#24)

* Recommend pipx or virtualenv installation

* Add 2.6 as a no-op upgrade

README.md

@@ -3,11 +3,13 @@
 This tool will help you make the changes necessary to upgrade your Baseplate.py
 service from one version to another.
 
-Install the upgrader on your development machine (outside any VMs, since this
-will be editing source code):
+The easiest way to use this tool is through `pipx` (`brew install pipx` on
+macOS):
 
-    pip3.7 install git+https://github.com/reddit/baseplate.py-upgrader
+    pipx run --spec git+https://github.com/reddit/baseplate.py-upgrader baseplate.py-upgrader ~/src/fooservice
 
-and then run it on a baseplate.py project you want to upgrade:
+You can also create a virtualenv and install it manually:
 
-    baseplate.py-upgrader ~/src/fooservice
+    python3.12 -m venv venv
+    venv/bin/pip install git+https://github.com/reddit/baseplate.py-upgrader
+    venv/bin/baseplate.py-upgrader ~/src/fooservice

baseplate_py_upgrader/__init__.py

@@ -45,11 +45,12 @@ def no_op_upgrade(
     "1.3": "1.4",
     "1.4": "1.5",
     "1.5": "2.0",
-    "2.0": "2.5",
-    "2.1": "2.5",
-    "2.2": "2.5",
-    "2.3": "2.5",
-    "2.4": "2.5",
+    "2.0": "2.6",
+    "2.1": "2.6",
+    "2.2": "2.6",
+    "2.3": "2.6",
+    "2.4": "2.6",
+    "2.5": "2.6",
 }
 
 # this is useful if we're dealing with pre-releases temporarily
@@ -75,6 +76,7 @@ def no_op_upgrade(
     "2.3": no_op_upgrade,
     "2.4": no_op_upgrade,
     "2.5": no_op_upgrade,
+    "2.6": no_op_upgrade,
 }