Completely remove mouse support

Since the version 0.7.0, fzf internally used Curses.getch() call to take user
input, which allowed it to support mouse input as well. However it has turned
out that Curses.getch() has introduced glitches that cannot be easily handled
(e.g. Try resize the terminal). So I finally decided that it's not worth the
trouble and drop the mouse support.

README.md

@@ -58,7 +58,6 @@ usage: fzf [options]
     -i                   Case-insensitive match (default: smart-case match)
     +i                   Case-sensitive match
     +c, --no-color       Disable colors
-        --no-mouse       Disable mouse
 
   Environment variables
     FZF_DEFAULT_COMMAND  Default command to use when input is tty
@@ -102,9 +101,6 @@ The following readline key bindings should also work as expected.
 If you enable multi-select mode with `-m` option, you can select multiple items
 with TAB or Shift-TAB key.
 
-You can also use mouse. Click on an item to select it or shift-click to select
-multiple items. Use mouse wheel to move the cursor up and down.
-
 ### Extended-search mode
 
 With `-x` or `--extended` option, fzf will start in "extended-search mode".