Include submodule for Mustache specifications.
Test that use all tests from Mustache specifications. The ones that fails in current mustache.js are skiped to not break the build.
Update README.md

Instruction for including sub module with Mustache specs.
Used fs.existsSync that doesn't exists in nodejs 0.6 that is used by travis for testing.
Merge pull request #301 from danielfagerstrom/topic/spec

Mustache specs