The .iohpid file is written in the working directory

[danielshub]

In iohub/client.py the .iohpid file is written in "rootScriptPath". If this directory is not writable, this causes the iohub client to crash. The XDG Base Directory Specification (http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html#variables) covers where these types of files should be saved and I think .iohpid should be saved in $XDG_RUNTIME_DIR since it is a runtime file and not a data file or a configuration file. I also think the standard naming for PID files in Linux would make the file called iohub.pid