change of exception list handling

"Exception" is quite an overloaded term, thus exception lists were
renamed to skip lists; even 'skip dicts', since their type changed, too.

README.md

@@ -15,7 +15,7 @@ Features:
 - fully configurable through global variables (options and mappings)
 - optional preserving of signs from other plugins
 - you can toggle the plugin per buffer
-- exception lists for filetypes and filenames
+- skip certain filetypes and filenames
 - good documentation
 
 - quick developer response! :-)
@@ -126,16 +126,16 @@ it:
 let g:signify_mapping_toggle = '<leader>gt'
 ```
 
-#### exception lists for filetypes and filenames
+#### skip certain filetypes and filenames
 
 If you want to disable Sy for certain kinds of filename or file types,
-you explicitely have to create exception lists:
+you explicitely have to create "skip dicts":
 
 Example:
 
 ```vim
-let g:signify_exceptions_filetype = [ 'vim', 'c' ]
-let g:signify_exceptions_filename = [ '.vimrc' ]
+let g:signify_skip_filetype = { 'vim': 1, 'c': 1 }
+let g:signify_skip_filename = { '/home/user/.vimrc': 1 }
 ```
 
 #### good documentation
@@ -169,8 +169,8 @@ let g:signify_mapping_prev_hunk = '<leader>gp'
 let g:signify_mapping_toggle_highlight = '<leader>gh'
 let g:signify_mapping_toggle           = '<leader>gt'
 
-let g:signify_exceptions_filetype = [ 'vim', 'c' ]
-let g:signify_exceptions_filename = [ '.vimrc' ]
+let g:signify_skip_filetype = { 'vim': 1, 'c': 1 }
+let g:signify_skip_filename = { '/home/user/.vimrc': 1 }
 
 let g:signify_sign_overwrite = 1
 

doc/signify.txt

@@ -114,8 +114,8 @@ Mapping for toggling line highlighting for lines containing changes.
 Mapping for toggling the plugin for the current buffer only.
 
 
-    let g:signify_exceptions_filetype = [ 'vim', 'c' ]
-    let g:signify_exceptions_filename = [ '.vimrc' ]
+    let g:signify_skip_filetype = { 'vim': 1, 'c': 1 }
+    let g:signify_skip_filename = { '/home/user/.vimrc': 1 }
 
 Don't activate the plugin for these filetypes and/or filenames.
 

plugin/signify.vim

@@ -139,20 +139,11 @@ function! s:start(path) abort
     execute 'sign place 99999 line=1 name=SignifyPlaceholder file='. a:path
   endif
 
-  " Check for exceptions.
-  if exists('g:signify_exceptions_filetype')
-    for i in g:signify_exceptions_filetype
-      if i == &ft
-        return
-      endif
-    endfor
+  if exists('g:signify_skip_filetype') && has_key(g:signify_skip_filetype, &ft)
+    return
   endif
-  if exists('g:signify_exceptions_filename')
-    for i in g:signify_exceptions_filename
-      if i == a:path
-        return
-      endif
-    endfor
+  if exists('g:signify_skip_filename') && has_key(g:signify_skip_filename, a:path)
+    return
   endif
 
   " New buffer.. add to list.