Add self-contained gometalinter build tooling.

tools/vendor/github.com/alecthomas/gocyclo/README.md

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+Gocyclo calculates cyclomatic complexities of functions in Go source code.
+
+The cyclomatic complexity of a function is calculated according to the
+following rules:
+
+     1 is the base complexity of a function
+    +1 for each 'if', 'for', 'case', '&&' or '||'
+
+To install, run
+
+    $ go get github.com/fzipp/gocyclo
+
+and put the resulting binary in one of your PATH directories if
+`$GOPATH/bin` isn't already in your PATH.
+
+Usage:
+
+    $ gocyclo [<flag> ...] <Go file or directory> ...
+
+Examples:
+
+    $ gocyclo .
+    $ gocyclo main.go
+    $ gocyclo -top 10 src/
+    $ gocyclo -over 25 docker
+    $ gocyclo -avg .
+
+The output fields for each line are:
+
+    <complexity> <package> <function> <file:row:column>
+