Added some tests for `cygapt.utils.rmtree` function

Clean up following specification paths iteratively or not:
    - No exists
    - No read permission
    - Symlink to a file
    - Symlink to a directory
    - Broken symlink
Fixed `cygapt.utils.rmtree`
Merge pull request #19 from alquerci/fix/utils/rmtree

Improved test suite for rmtree
Improved the test suite run 10x faster
Merge pull request #17 from alquerci/ipv/test_suite

Make the test suite run 10x faster
Fix platform detection for 32 or 64 bit Cygwin

If we're running in Cygwin's python, check sys.maxsize to determine
the Cygwin platform.

If we're running in Windows python, the python platform may not match
the Cygwin platform, so read the PE header of cygwin1.dll to determine
the Cygwin platform.

References:
http://en.wikibooks.org/wiki/X86_Disassembly/Windows_Executable_Files#File_Format
https://github.com/file/file/blob/b3f55f53/magic/Magdir/msdos#L79