Multiple platforms setup

[Shaofanl]

Changes:

• Using sys.platform to determine the platform is more professional and more common in Python setup than using platform.system(). For more details: When to use os.name, sys.platform, or platform.system?
• Also I raise an exception when the platform is not supported. (When installed on an unsupported platform, the original setup will show NameError: name 'package_data' is not defined, which is quite confusing.)
• I add the support on Linux and Cygwin.

Things that I don't know how to fix:

• After modifying setup.py, I use python setup.py install on both Linux and Cygwin. And I can see the installation works (I will show the result on cygwin, which is similar to the result on Linux):

running install
running bdist_egg
running egg_info
creating pySBOL.egg-info
writing pySBOL.egg-info/PKG-INFO
writing top-level names to pySBOL.egg-info/top_level.txt
writing dependency_links to pySBOL.egg-info/dependency_links.txt
writing manifest file 'pySBOL.egg-info/SOURCES.txt'
reading manifest file 'pySBOL.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
writing manifest file 'pySBOL.egg-info/SOURCES.txt'
installing library code to build/bdist.cygwin-2.0.4-x86_64/egg
running install_lib
running build_py
creating build
creating build/lib
creating build/lib/sbol
copying sbol/sbol.py -> build/lib/sbol
copying sbol/sbol_test.py -> build/lib/sbol
copying sbol/init.py -> build/lib/sbol
creating build/lib/sbol/examples
copying sbol/examples/inspect_sbol_file.py -> build/lib/sbol/examples
copying sbol/examples/test.xml -> build/lib/sbol/examples
creating build/bdist.cygwin-2.0.4-x86_64
creating build/bdist.cygwin-2.0.4-x86_64/egg
creating build/bdist.cygwin-2.0.4-x86_64/egg/sbol
creating build/bdist.cygwin-2.0.4-x86_64/egg/sbol/examples
copying build/lib/sbol/examples/inspect_sbol_file.py -> build/bdist.cygwin-2.0.4-x86_64/egg/sbol/examples
copying build/lib/sbol/examples/test.xml -> build/bdist.cygwin-2.0.4-x86_64/egg/sbol/examples
copying build/lib/sbol/sbol.py -> build/bdist.cygwin-2.0.4-x86_64/egg/sbol
copying build/lib/sbol/sbol_test.py -> build/bdist.cygwin-2.0.4-x86_64/egg/sbol
copying build/lib/sbol/init.py -> build/bdist.cygwin-2.0.4-x86_64/egg/sbol
byte-compiling build/bdist.cygwin-2.0.4-x86_64/egg/sbol/examples/inspect_sbol_file.py to inspect_sbol_file.pyc
byte-compiling build/bdist.cygwin-2.0.4-x86_64/egg/sbol/sbol.py to sbol.pyc
byte-compiling build/bdist.cygwin-2.0.4-x86_64/egg/sbol/sbol_test.py to sbol_test.pyc
byte-compiling build/bdist.cygwin-2.0.4-x86_64/egg/sbol/init.py to init.pyc
creating build/bdist.cygwin-2.0.4-x86_64/egg/EGG-INFO
copying pySBOL.egg-info/PKG-INFO -> build/bdist.cygwin-2.0.4-x86_64/egg/EGG-INFO
copying pySBOL.egg-info/SOURCES.txt -> build/bdist.cygwin-2.0.4-x86_64/egg/EGG-INFO
copying pySBOL.egg-info/dependency_links.txt -> build/bdist.cygwin-2.0.4-x86_64/egg/EGG-INFO
copying pySBOL.egg-info/top_level.txt -> build/bdist.cygwin-2.0.4-x86_64/egg/EGG-INFO
zip_safe flag not set; analyzing archive contents...
creating dist
creating 'dist/pySBOL-1.0.0b1-py2.7.egg' and adding 'build/bdist.cygwin-2.0.4-x86_64/egg' to it
removing 'build/bdist.cygwin-2.0.4-x86_64/egg' (and everything under it)
Processing pySBOL-1.0.0b1-py2.7.egg
Removing /usr/lib/python2.7/site-packages/pySBOL-1.0.0b1-py2.7.egg
Copying pySBOL-1.0.0b1-py2.7.egg to /usr/lib/python2.7/site-packages
pySBOL 1.0.0b1 is already the active version in easy-install.pth
Installed /usr/lib/python2.7/site-packages/pySBOL-1.0.0b1-py2.7.egg
Processing dependencies for pySBOL==1.0.0b1
Finished processing dependencies for pySBOL==1.0.0b1

But when I import the sbol from python, I got:

Traceback (most recent call last):
File "", line 1, in
File "build/bdist.cygwin-2.0.4-x86_64/egg/sbol/init.py", line 3, in
File "build/bdist.cygwin-2.0.4-x86_64/egg/sbol/sbol.py", line 17, in
ImportError: No module named libsbol

I guess the libsbol is not installed correctly. Hope you can work it out. Otherwise just remove the linux2 and cygwin support in setup.py.