Avoid use of nested bin for yarn compatibility

[rgoldfinger]

Yarn has different semantics for handling nested bins (i.e. it doesn't handle them). See yarnpkg/yarn#760. This makes this package compatible with yarn by avoiding the use of the bin.

[coveralls]

Coverage remained the same at 95.146% when pulling b65f1bc on rgoldfinger:yarn-compatibility into 069d80a on tarmolov:master.

[tarmolov]

It seems that it's a yarn bug and the pr yarnpkg/yarn#1210 should fix it.
It's better to wait a little.

[rgoldfinger]

From my reading, hoisting binaries has questionable semantics that the yarn authors are not eager to support, and that PR seems to be going nowhere. Since it's easy enough to avoid relying on this feature of npm, I'm hoping that you'll be open to avoiding it and making this package compatible with yarn.

Thank you, by the way, for the great package. We rely on it heavily and are holding off on yarn because we don't want to lose it.

[rjmunro]

IMHO, unless there is reason for the user to call the node_modules/.bin/git-hooks script directly from time to time, it seems wrong to include it in the bin section of package.json.

[tarmolov]

Just published 1.1.7