added requirements file and slugify module
WIP parsing Evernote post-note to WpPost - working on parsing metadata section - finished with simple fields
added Evernote NoteLink parser
changed WpPost fromEvernote initialization to accept note guid instead of note content.

using mock.patch to mock real evernote client in unit tests.
refactored Evernote note to WordPress object (Post or ImageAttachment)

to pass through a factory that performs partial parsing to decide on type,
followed by completing parsing using the determined type,
including recusrive parsing of parent / thumbnail note-links
(but not yet body links).