Change Repository.listTree to accept params, added showFile

Generated with CoffeeScript 1.7.1 instead of 1.6.3, caused a lot of file changes. Feel free to pull the important files out into another commit. The key changes are in ProjectRepository.coffee/.js
```coffeescript
# === Tree
  listTree: (projectId, params = {}, fn = null) =>
    @debug "Projects::listTree()"
    if 'function' is typeof(params)
      fn = params
      params = {}
    @get "projects/#{parseInt projectId}/repository/tree", params, (data) => fn data if fn

  # == Files
  showFile: (projectId, params, fn = null) =>
    @debug "Projects::showFile()", params
    if params.file_path and params.ref
      @post "projects/#{parseInt params.projectId}/repository/files", params, (data) => fn data if fn
```