Use fixed sha1 for building shapeless 2.

The latest commits in scala-2.11.x broke spray. Let's use fixed sha1
until we figure out how to build both shapeless 1.2.4 (dependency of
spray) and shapless 2 in community build.
Merge pull request #32 from gkossakowski/shapeless-regression

Use fixed sha1 for building shapeless 2.