This adds hub version to crash report. It includes refactoring of hub version to the `version` package for reusability in `commands` package and `github` package.

GNU find(1)'s -not operator is not POSIX compliant.  Use ! operator
instead in order to work with other find(1) implementations.

The best way to run this is in the GitHub for Windows shell.

This makes our build scripts even more simpler. To build with autoupdate, run `go build -tags autoupdate`

If there’s no GOPATH set up locally, Go won’t be able to find sub packages. This is due to changes in https://github.com/github/hub/commit/af9163b699b34ffa167ef99853ff2f7374d7b01a.

Use the `-ldflags` to change version at the linker. See http://golang.org/cmd/ld.

Issue: https://github.com/github/hub/issues/672#issuecomment-62040388

We need to run the packaging script for every platform using a Vagrant box. During the packaging step, cukes are run. However, the workspace is shared between host and the Vagrant box. Instead of cleaning up the built binary for each platform, build it into a temporary dir.

Old `script/bootstrap` & `script/build` were unfriendly to Go newbies
because they require the user having GOPATH set in their environment,
and either `godep` installed or `hg` to be able to fetch godep.

However, since dependencies are vendored, we don't have any real build
dependencies except Go itself.

- `script/bootstrap` now checks Go and installs Ruby test bundle
- `script/build` skips compiling if binary is up to date
- `script/test` runs both Go and Cucumber test suites