feat(errors): extracted out from RequireState#addNodeIfNeeded
feat(errors): extracted from VinylNodeCollection#finalizeNode
feat(errors): added error messages and fixed #11
Merge pull request #22 from tomchentw/organize-error-message

Organize error message
refactor(VinylNodeCollection): rename _buildDependencies
refactor(SuperNode): rename _filepathMatcher
refactor(SuperNode): rename _filepathMatchedNodes
refactor(RequireState): rename _inRequireStates
refactor(RequireState): rename _keyPathAdded
refactor(RequireState): rename _pathsChanged
refactor(RequireState): rename _nothingChanged
refactor(RequireState): rename _totalBufferSize
refactor(RequireState): rename buildDependencies
refactor(RequireState): rename needRequireOrInclude
refactor(*): rename RequireState#addNodeIfNeeded
refactor(Node): rename _resolveKeyPath
refactor(Node): rename pathMatches
refactor(Node): rename buildDependencies
refactor(*): rename engines to _engines
refactor(*): rename engine_extensions to _engine_extensions