add "-source" option for gocode autocompletion

[kyoh86]

Now, ycmd cannot complete golang external packages.
ycmd must enable source importer with -source flag.

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This change is 

[kyoh86]

for your reference: mdempsky/gocode#32 (comment)

[bstaletic]

What worries me about this is the performance impact it imposes. However, I have never used go, so I would like to hear from go users if this is something we really want to enable by default.

[bstaletic]

Looking at the tests, something is clearly broken here. 3 out of 6 are broken because the expected call in the tests doesn't have -source, but the other three say that gocode panicked, even the basic completion test failed because there are syntax errors in the file.

[kyoh86]

oh I see, sorry. I'll fix it later.

[kyoh86]

gocode panicked

Sorry, I cannot reproduce the error on local...

[Valloric]

@kyoh86

Sorry, I cannot reproduce the error on local...

We rely on CI bots to ensure all tests pass. If a PR cannot pass tests on our CI infrastructure, it cannot be merged.

[micbou]

PR seems abandoned. Closing.