Make pexpect.py Python 3 Compatable

Warning changes have been not tested against Python 2!
If the code works in Python2 then this patch resolves Buildozer Issue #131.
https://github.com/kivy/buildozer/issues/131
Specs doc revision
fix for pathing issue when android.p4a_dir is defined (not using the default one downloaded by buildozer) and entries in android.library_references use relative paths from source.dir
Test in file_rename if target directory exists.

This is an attempt to give a reasonable error message in cases where
we are about to crash.  In particular, when android.sdk_path has a
path that does not exist, buildozer should provide a hint as to what
might have gone wrong.
backport android version check fixes from @monkut. Closes #137. Closes #143
Merge pull request #144 from droundy/master

Test in file_rename if target directory exists.
Merge pull request #139 from excessivedemon/master

Fix for android.library_references path issue
Merge pull request #134 from dessant/patch-1

Specs doc revision
Merge pull request #133 from FeralBytes/master

Make pexpect.py Python 3 Compatable
bump to 0.16
bump to 0.17-dev
Merge branch 'master' of ssh://github.com/kivy/buildozer
bump to 0.17
bump to 0.17-dev
added example to requirements
Merge pull request #148 from chozabu/clarify_reqs_example

added example to default.spec requirements showing comma seperation