Ship assets in compiled binary.

- utility/embed-static.sh, get called in Makefile to create go map from files
- web/blob/blob.go implements http Handle for serving the files from the map
- web/status.go uses blog.GetFile() to get the template file

The assets are gzipped and decompressed on demand.
Replace popd/pushd because travis' /bin/sh doesn't support it.
Use constants for blob bucket keys.
Detect mime type on runtime instead of hardcoding.
Added vim-common to travis build environment.

vim-common includes `xxd` which we use to hexdump files for package blob.
Enable debugging (set -x) on embed-static.sh.
Remove echo -e because it's not available on Travis.

Instead, files.go gets piped through gofmt.
Merge pull request #87 from prometheus/feature/build-in-static-assets

Ship assets in compiled binary.