Escape leading periods on packageignore list (#373)
Escape leading periods on packageignore list (#373)

Otherwise, the `.` is interpreted as a period in a regular expression,
  which matches every literal character, causing some packages deep in
  the `node_modules/` hierarchy to be ignored for no reason.

For example, if we ignore `.git`, then a package like `foo-git` will be
excluded from the final package.

Signed-off-by: Juan Cruz Viotti <8493db2a4f45d66df375afe12f7eba59fe1c8d78@gmail.com>
cedricve/etcher,resin-io/herostratus,resin-io/resin-etcher,resin-io/herostratus,resin-io/etcher,cedricve/etcher,cedricve/etcher,resin-io/etcher,resin-io/etcher,resin-io/etcher,resin-io/etcher,resin-io/resin-etcher