auto parse deps

[haoxins]

if I add one dep in Goopfile, such as

github.com/gohttp/app #5fe28eda25acc96b48d8f2ddb651ea9104cc3e7c

I want to do goop install --auto-parse

and the deps of github.com/gohttp/app will be parsed, and saved to Goopfile

so, the result will be:

github.com/gohttp/app #5fe28eda25acc96b48d8f2ddb651ea9104cc3e7c
github.com/justinas/alice #e82c7d9ec9ebfd83e90d4fd39ce934f5fc0b0b5f
github.com/bmizerany/pat #b8a35001b773c267eb260a691f4e5499a3531600

[haoxins]

sorry, forget Goopfile.lock