Fix error when interprogram-cut-function unset
Fix error: wrong-type-argument number-or-marker-p nil
Use overlay for storing kill candidate and change +/-

which also fixes breakage in emacs trunk, which has implemented
universal-argument using set-temporary-overlay-map.
Call interprogram-cut-function in easy-kill-forward
Various bug fixes and improvements
Rename easy-kill-forward/backward to easy-kill-enlarge/shrink

and make them extensible via property easy-kill-enlarge.
Give overlay by easy-kill-candidate higher priority

to avoid shadowing by other modes such as hl-line-mode. Doc fix.
Restore the ability to inspect char properties for URLs

with new function easy-kill-on-url.
New function easy-kill-adjust-candidate and doc fix
Minor tweaks to easy-kill-on-url
Tweak the definition of thing `region'
New command easy-kill-region to kill current selection
Doc fix and release v0.7.0
Some string and comment fixes
Make function easy-kill-candidate always return string
Fix error: (args-out-of-range 1009 1035)

Such errors could happen when easy-kill is active and emacsclient
opens a new buffer.
Consolidate all kill features in easy-kill-thing

Rename easy-kill-enlarge to easy-kill-expand.
Add lispy treatment for +/- on list and sexp
Replace `enlarge' with `expand' in strings and comments
New command easy-kill-mark-region