Improved EasyGrep startup from arbitrary locations

EasyGrep now looks for the EasyGrepFileAssociations file much more intelligently.
Suppressed an issue when vimgrep reported that a swap file could not be opened.
Renamed the test suite to casesensitivity.
Added ack-grep to GrepProgram.
Added note about the EasyGrepRepository to the docs.
Merge branch 'master' of https://github.com/dkprice/vim-easygrep