Update talk slugs to preserve URLs

PyVideo URLs are generated based on their talk titles by default. This
behavior can be overridden by setting the talk's `slug` attribute. This
commit sets slug values for any talk titles updated as part of PR 1154
to preserve existing links to these talks on pyvideo.org.

north-bay-python-2019/videos/a-gradual-introduction-to-types-laura-hampton-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "a-gradual-introduction-to-types-laura-hampton-north-bay-python-2019",
   "speakers": [
     "Laura Hampton"
   ],

north-bay-python-2019/videos/a-hunting-we-will-go-debugging-pytest-with-django-cris-ewing-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "a-hunting-we-will-go-debugging-pytest-with-django-cris-ewing-north-bay-python-2019",
   "speakers": [
     "Cris Ewing"
   ],

north-bay-python-2019/videos/from-prison-to-python-shadeed-wallace-stepter-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "from-prison-to-python-shadeed-wallace-stepter-north-bay-python-2019",
   "speakers": [
     "Shadeed Wallace-Stepter"
   ],

north-bay-python-2019/videos/how-to-build-a-terrible-robot-paloma-fautley-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "how-to-build-a-terrible-robot-paloma-fautley-north-bay-python-2019",
   "speakers": [
     "Paloma Fautley"
   ],

north-bay-python-2019/videos/keep-calm-and-mind-the-docs-andrea-kao-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "keep-calm-and-mind-the-docs-andrea-kao-north-bay-python-2019",
   "speakers": [
     "Andrea Kao"
   ],

north-bay-python-2019/videos/see-cpython-run-getting-to-know-your-python-interpreter-james-bennett-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "see-cpython-run-getting-to-know-your-python-interpreter-james-bennett-north-bay-python-2019",
   "speakers": [
     "James Bennett"
   ],

north-bay-python-2019/videos/the-secret-life-of-python-steve-dower-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "the-secret-life-of-python-steve-dower-north-bay-python-2019",
   "speakers": [
     "Steve Dower"
   ],

north-bay-python-2019/videos/to-with-passwords-jacob-kaplan-moss-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "to-with-passwords-jacob-kaplan-moss-north-bay-python-2019",
   "speakers": [
     "Jacob Kaplan-Moss"
   ],

north-bay-python-2019/videos/what-is-a-coroutine-anyway.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "what-is-a-coroutine-anyway-amethyst-reese-north-bay-python-2019",
   "speakers": [
     "Amethyst Reese"
   ],

north-bay-python-2019/videos/what-is-a-plc-and-how-do-i-talk-python-to-it-jonas-neubert-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "what-is-a-plc-and-how-do-i-talk-python-to-it-jonas-neubert-north-bay-python-2019",
   "speakers": [
     "Jonas Neubert"
   ],

north-bay-python-2019/videos/writing-a-peg-parser-for-fun-and-profit-guido-van-rossum-north-bay-python-2019.json

@@ -14,6 +14,7 @@
       "url": "https://2019.northbaypython.org/schedule/"
     }
   ],
+  "slug": "writing-a-peg-parser-for-fun-and-profit-guido-van-rossum-north-bay-python-2019",
   "speakers": [
     "Guido van Rossum"
   ],