Move test modules to a common module

With this change, the project will follow the directory structure
specified in:
http://guide.python-distribute.org/creation.html
fix test method hiding another by using the same name
fspath.working_directory() and replace tempdir with temp_dir
use abc.ABCMeta, also extract locate() as a function
remove External.create - duplicate of .set_content
sublime project file
Fake: in-memory external
Hierarchy.child(name) -> Hierarchy / name
remove u before strings (u'...' -> '...')

reason: it is unnecessarily ugly
.content become a read-write property
locate: update doc strings
FsPath.path is public
TestHierarchy -> Hierarchy
copy_to method - simple implementation, that do not work with externals not fitting in memory
FsPath.copy_to - multiple partial reads on bigger files
fix test dependecy and PEP8 compliance
fake: extra /-s ignored in paths