Second (smaller) set of native core functions

This rounds out the first pass at a set of core functions, adding
some that were not in the first PR.

From here I'm working on a contrib.seq and contrib.io module to
hold less obvious but maybe interesting native functions that can
move to core if desired.

This should also close out issure #150 asking for some core
functions like these.
slightly cleaner version of drop-while, could use yield-from when ready
One more commit to change the test for Python 2/3 to a macro

Note that this can't use the macro in hy.core.macros so there
is a local copy in language.hy
finally fixed access to hy.core.macros here. have to explicitly require them
Various setup.py enhancements.

- PEP8 fixes
- Use setuptools.find_packages()
- Update PyPI classifiers
- Update website URL
- Install the argparse module in Python 2.6 and before
- Delete the duplicate rply in install_requires. With the PyPI
  version, tests are failed.
Merge branch 'patch-1' of https://github.com/berkerpeksag/hy into berkerpeksag-patch-1