Clarify names in salsa example

The ingredients lists sound like actual mild and hot salsa already. By making more intuitive and informative names, we can model variable naming best practices and make it easier to follow the example. To do that, I edited both the code and the surrounding comments and text.

Author: ndporter

_episodes/04-lists.md

@@ -129,31 +129,31 @@ does not.
 > the list value, it will change for both variables!
 >
 > ~~~
-> salsa = ['peppers', 'onions', 'cilantro', 'tomatoes']
-> my_salsa = salsa        # <-- my_salsa and salsa point to the *same* list data in memory
-> salsa[0] = 'hot peppers'
-> print('Ingredients in my salsa:', my_salsa)
+> mlld_salsa = ['peppers', 'onions', 'cilantro', 'tomatoes']
+> hot_salsa = mild_salsa        # <-- mild_salsa and hot_salsa point to the *same* list data in memory
+> hot_salsa[0] = 'hot peppers'
+> print('Ingredients in mild salsa:', mild_salsa)
 > ~~~
 > {: .language-python}
 >
 > ~~~
-> Ingredients in my salsa: ['hot peppers', 'onions', 'cilantro', 'tomatoes']
+> Ingredients in mild salsa: ['hot peppers', 'onions', 'cilantro', 'tomatoes']
 > ~~~
 > {: .output}
 >
 > If you want variables with mutable values to be independent, you
 > must make a copy of the value when you assign it.
 >
 > ~~~
-> salsa = ['peppers', 'onions', 'cilantro', 'tomatoes']
-> my_salsa = list(salsa)        # <-- makes a *copy* of the list
-> salsa[0] = 'hot peppers'
-> print('Ingredients in my salsa:', my_salsa)
+> mild_salsa = ['peppers', 'onions', 'cilantro', 'tomatoes']
+> hot_salsa = list(mild_salsa)        # <-- makes a *copy* of the list
+> hot_salsa[0] = 'hot peppers'
+> print('Ingredients in mild salsa:', mild_salsa)
 > ~~~
 > {: .language-python}
 >
 > ~~~
-> Ingredients in my salsa: ['peppers', 'onions', 'cilantro', 'tomatoes']
+> Ingredients in mild salsa: ['peppers', 'onions', 'cilantro', 'tomatoes']
 > ~~~
 > {: .output}
 >