Buffer rewritten to use gapbuffer. Broken right now.
Added Up/Down movement methods (uses experimental slicing).
Nothing important.
Merge remote-tracking branch 'parent/master'

Conflicts:
	src/iota/buffer.rs
Merge branch 'master' into gapbuffer

Conflicts:
	src/iota/buffer.rs
Added lookup table to support multiple marked indices. Changed line calculation algorithm. Integrated consistent line offset as traversing vertically. Broke view.rs.
Added Lines iterator to buffer, should be useful in drawing the buffer to the screen.
Still busted, but got a good draft of the interaction between view.rs and buffer.rs. Removed cursor.rs completely.
Finalized API for buffer. The whole thing should work now but I still have to write tests to confirm.
Updated lines_from to take a mark instead of a uint.
Changed offset_mark interface to use direction.
Updated tests for view.
Merge remote-tracking branch 'parent/master'

Conflicts:
	src/iota/buffer.rs
Merge branch 'master' into gapbuffer

Conflicts:
	src/iota/cursor.rs
An incomplete attempt to incorporate the log into this branch. Currently doesn't pass the borrow checker.
Merge remote-tracking branch 'parent/master'
Merge branch 'master' into gapbuffer
All tests passed.
Finished implementing gapbuffer.
Fixed a bug in undo/redo.