book: let grow() accept the growth parameter

[tshepang]

I found the arbitrary 10 surprising. A better method name, in such a case, would be grow_by_10 :)

[rust-highfive]

r? @nikomatsakis

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[Manishearth]

@bors: r+ rollup

I personally am okay with having overly specific examples like grow_by_10; sometimes having the complexities required to make a method real-world-ish make it unsuitable for docs.

But in this case it seems minor, and also introduces how self methods can take more parameters.

[bors]

📌 Commit 07afd04 has been approved by Manishearth