Fix: atom-racer does not need to create temporary files

[mindsbackyard]

atom-racer creates temporary files to provide completion even for unsafed content. This results in a lot of writes to the disk and is unnecessary. The racer command allows to pass a subsitute file whose content will be used instead of the file completion is invoked for (its location is used nevertheless). Instead of specifying a real substitute file '-' is passed and the contents are read from stdin. This also removes the 'temp' dependency.

[bronson]

Love this. Hope it can be merged.

[dszakallas]

why isn't this merged yet?

[Xaeroxe]

merged into racer-plus package here https://github.com/Xaeroxe/atom-racer