Added windows symlink support

This package implements the windows equivalent of os.Symlink() and os.Readlink(). It also adds a wrapper for creating symlinks for both linux and windows. Signature is the same as the standard os functions.
wrong nr of assigned variables
Reaname functions

* rename Symlink() to New() and Readlink() to Read()
added a thin wrapper for reading a password
moved file to match package name
Merge pull request #3 from mattyw/read-password

readpass: new package
clean up the symlink stuff to use the standard windows syscall structure
fix up the build
Merge pull request #1 from natefinch/windows-symlink-support

Windows symlink support
make the tests actually run
Merge pull request #2 from natefinch/windows-symlink-support

make the tests actually run
Fixed tests and access denied error
ran gofmt
use syscall's existing createfile and closehandle.  Make GetLongPath unexported, and use it internally.
one more getlongpath on the way out
remove spurious log statement
Merge pull request #3 from natefinch/windows-symlink-support

a little tweak to unexport getlongpath
Added GENERIC_EXECUTION constant
Added comment on GENERIC_EXECUTION
chmod not supported by windows