New Shell.Builder and Shell.Interactive classes
waitForIdle() deadlock

waitForIdle() could be called synchronized, which would prevent the idle
state from occuring
Revert "added clearEnvironment function, added environment support to SH shell, updated documentation"

This reverts commit 645de9b474469225a53f1b4aeee9bdcac7f2d71a.
Revert "added support for custom environment"

This reverts commit 7014b5ef8650b851e44497c5518bc542ecd5208d.
Merge branch 'master' of https://github.com/Chainfire/libsuperuser