Added a short circuit check

[ideasasylum]

I'm not sure if this is generally useful but I've found it very important. This checks for accidental short-circuits often used in debugging, e.g. Rails views, to force a particular state.

Statements like,

if true || something
if false && something

can be used when developing to force a particular condition but they're almost certainly an error if committed to Git.

I based this check & tests on the debugger check so I hope I haven't missed anything.

[coveralls]

Coverage increased (+0.03%) to 96.279% when pulling 4fe1a95a933c3ebe0808e70d05cec545400c95b7 on ideasasylum:master into 860ce02ce2a1c3523e14297682a06f1402292c18 on jish:master.

[mpapis]

oh, I missed to update readme, there is now easy way to create external plugins => https://github.com/jish/pre-commit/blob/master/lib/pre-commit/cli.rb#L31 - maybe try to make it an external plugin and we can add it to https://github.com/pre-commit-plugins/ and list it in the readme :)

code itself LGTM

[dannysmith]

@ideasasylum Did you ever make a plugin out of this?