Issue #11

* add new text property `wgrep-fn-*' prepare for file renaming
* parser for helm-grep
* remove dependencies from wgrep-ack.
* make obsolete `wgrep-acceptable-modes' no need to check such thing.
* wgrep-to-grep-mode -> wgrep-to-original-mode
  may back to wrong mode and map
* fix unable cleanup temporary buffer.
* mark ignore if output result is not a valid grep line
  ex: Binary file.
remove `wgrep-ginore' property from context output.
fix helm grep buffer, which does not have a footer
fixbug check `re-search-backward' return value #13
fix helm grep again
fix version
bugfix #17
Stall program when change read-only file line.