resolve symlinks in local files

the tar libraries choke when checking valid
filenames because they don't resolve symlinks
Merge branch 'hotfix/1.0.2'
Merge pull request #245 from ptone/find-links-symlinks

resolve symlinks in local files
Merge branch 'release/1.1'
Merge branch 'release/1.2'
Merge branch 'release/1.2.1'
Merge branch '1.3.X'
Merge branch '1.3.X'
Display hashdigest instead of hash object upon failure.
add missing PermissionError import
add note about quoting requirement specifiers
quote our examples that use > or <
short test cache path segments to undercut windows path length
don't install or build wheels for distribute in python3
Merge pull request #937 from qwcode/ignore_reqs

don't install or build wheels for distribute in python 3
Added a pypip.in badge with the latest version.
write pip delete marker into global build dir upon creation
Merge pull request #948 from qwcode/global_build_cleanup

write pip delete marker into global build dir upon creation
Fixed typo in some help messages
Merge pull request #955 from Zearin/master

Fixed typo in some help messages