minor typos

Author: dstndstn

_episodes/07-errors.md

@@ -227,7 +227,7 @@ Variable name errors come with some of the most informative error messages,
 which are usually of the form "name 'the_variable_name' is not defined".
 
 Why does this error message occur?
-That's harder question to answer,
+That's a harder question to answer,
 because it depends on what your code is supposed to do.
 However,
 there are a few very common reasons why you might have an undefined variable.

_episodes/09-debugging.md

@@ -151,7 +151,7 @@ Replacing random chunks of code is unlikely to do much good.
 if you got it wrong the first time,
 you'll probably get it wrong the second and third as well.)
 Good programmers therefore
-*change one thing at a time, for a reason*
+*change one thing at a time, for a reason*.
 They are either trying to gather more information
 ("is the bug still there if we change the order of the loops?")
 or test a fix

_episodes/10-cmdline.md

@@ -585,7 +585,7 @@ $ python count_stdin.py small-01.csv
 ~~~
 {: .bash}
 
-i.e., to forget the `<` character that redirect the file to standard input.
+i.e., to forget the `<` character that redirects the file to standard input.
 In this case,
 there's nothing in standard input,
 so the program waits at the start of the loop for someone to type something on the keyboard.
@@ -985,7 +985,7 @@ the program now does everything we set out to do.
 >
 > Write a program called `check_arguments.py` that prints usage
 > then exits the program if no arguments are provided.
-> (Hint) You can use `sys.exit()` to exit the program.
+> (Hint: You can use `sys.exit()` to exit the program.)
 >
 > ~~~
 > $ python check_arguments.py