Add initial version of CPAN skeleton. Haven't tested much yet.
Fix a couple errors in cpan.py and make it use final package name for directory name.
Only create directory if it didn't already exist
Use set for dependencies to avoid duplicates
Added support for recursive recipe creation, and we no longer add
dependencies that are part of the Perl core (unless a specific version
is specified).
Add lots of memoization to reduce repeated queries to metacpan
Make PERL_CORE check more lenient (any version means its not added to requirements), and prevent duplicates with --recursive.
Remove some memoization that is no longer necessary after fixing duplication with recursive recipe generation.
More tweaks to skip duplicates
Remove versions from dependencies in CPAN recipes because they're minimum versions.
Make sure build_depends has everything in run_depends for CPAN skeletons.
Add support for recursively building recipes of dependencies if they're in the current directory.
Switch to filtering develop requirements instead of test, and use included memoized decorator.
Add test script creation to cpan skeleton.
Fix typo in Windows CPAN run_test.bat skeleton.
Drop os.path prefix from os.path.abspath, since it's imported.
Merge branch 'master' into cpan_skeleton
Python 2/3 compatibility first steps for build.py

Also added module documentation and sorted imports.
Add docstrings for all of the functions in build.py
Fixed prefix_files being used as both a function and a variable in build.py