[PATCH 034/153] expanduser/resolve the default ~/.pex/install dir
[PATCH 034/153] expanduser/resolve the default ~/.pex/install dir

RB_ID=159381

(sapling split of 6b2727e665f09e426bb172ed364d591ec2a52920)

(sapling split of f6f3d7dbcb68da22c633a11923f5171461e2c924)
pombredanne/pex,mzdanieltest/pex,sixninetynine/pex,jamesbroadhead/pex,jamesbroadhead/pex,URXtech/pex,URXtech/pex,sixninetynine/pex,rouge8/pex,kwlzn/pex,snyaggarwal/pex,rouge8/pex,pantsbuild/pex,kwlzn/pex,snyaggarwal/pex,pombredanne/pex,mzdanieltest/pex,pantsbuild/pex,jsirois/pex,jsirois/pex