bootstrap: setup GOPATH if it isn't already set.

This variable is a bit of a mystery to non-Go developers and it's
unclear how you set it up properly. As a result, if it's not set let's
set everything up how Go likes it. Ignore the `src` directory that
we're creating now.

This will also help keep the Homebrew formula simpler.

Closes #388.

.gitignore

@@ -16,3 +16,5 @@ obj-*
 
 rpm/BUILD*
 rpm/*RPMS
+
+src

script/bootstrap

@@ -1,6 +1,13 @@
 #!/bin/sh
 set -e
 
+if [ -z "$GOPATH" ]; then
+  export GOPATH="$(pwd)"
+  mkdir -p src/github.com/github
+  [ -h src/github.com/github/git-lfs ] ||
+    ln -s "$GOPATH" src/github.com/github/git-lfs
+fi
+
 script/fmt
 rm -rf bin/*
 go run script/*.go -cmd build "$@"