Skein staging directory should be configurable #237
Description
Currently, skein staging directory defaults to $HOME/.skein . There can be situations where we have to configure the staging directory path to a different location. For example, if there is not enough space left in $HOME to accommodate the staging files, we may have to configure it to a different location.
The approach I am thinking is to use an environment variable SKEIN_STAGING_DIR for this purpose. If $SKEIN_STAGING_DIR is set, then $SKEIN_STAGING_DIR/.skein will be used as the staging directory. Otherwise, fallback to $HOME/.skein