Removed passive voice from 7 examples

[budziq]

• Generate random numbers within a range
• Generate random numbers with normal distribution
• Generate random values of a custom type
• Encode a string as application/x-www-form-urlencoded
• Remove fragment identifiers and query pairs from a URL
• Make a HTTP GET request
• Download a file to a temporary directory

Connected with: https://github.com/brson/rust-cookbook/issues/139

[dtolnay]

Nicely done! This is a great improvement.

As you do the rest of these, pay attention to how the beginning of each sentence provides information that immediately puts the remainder of the sentence in context. Here is an analysis of one from this PR. Notice how the new sentence is clear because you understand the significance of each piece as you read it, while the old sentence is unclear because you need to read until the very end to find out what the sentence is trying to say.

Before

A tuple `(i32, bool, f64)`—I don't know what this example is about
and variable—still don't know
of user defined type—doesn't the user define the type of all variables?
`Point` are—more like "get to the point," am I right?
randomly generated—oh so it randomly generates things

After

Randomly generates—ok this example is about randomly generating something
a tuple `(i32, bool, f64)`—makes sense, this is what it generates
and variable of user defined type—neat, not limited to generating builtin types
`Point`—key thing to look for in the code