add new unstable feature  to fit  local project usage

there is test under cmd/test/get_test.go

example:

Suppose you are under the ~/testproject directory. and mkdir src/test as your own package.your path will be like ~/testproject/src/test.
Go to ~/testproject/src/test and touch file main.go with the content bellow:

	package main

	import (
	        "fmt"
	        "github.com/ggaaooppeenngg/TEST"
	)

	func main() {
	        fmt.Println(TEST.TEST)
	}

Go to ~/testproject, and run command `gopm gen -l` to generate local .gopmfile like:

	[res]
	include = 

	[project]
	localPath = ~/testproject

	[deps]
	github.com/ggaaooppeenngg/TEST = 

Then add run command and target for build. and .gopmfile will be like:

	[target]
	path= ~/testproject/test
	[res]
	include = 

	[project]
	localPath = ~/testproject

	[run]
	cmd = go run ~/testproject/src/test/main.go

	[deps]
	github.com/ggaaooppeenngg/TEST = 

*cmd* is flexable for you can command like `revel app` and other command rather than `go run ` .
Then type `gopm get -l`, you
 can find ~/testproject/src/github.com/ggaaooppeenngg/TEST, it means the package has been downloaded depends on .gopmfile.

Now  type `gopm run -l`
See what happens! It prints `TEST`. 
You can run `gopm run -l ` anywhere under the local project gopath, it will recursively find the  .gopmfile with value project and run . this feature does not work under the windows os.


codereview:

      It seems that the global var  `isHasGopath` is not used.
      It seems download work is single-thread , why not use goroutine?