[users/users_files] add exclude_pat to user files (closes #178)

pillar.example

       # execution bit for example.
       file_mode: keep
       sym_mode: 640
+      exclude_pat: "*.gitignore"
 
   ## Absent user
   cuser:

users/user_files.sls

 {%- set user_files_template = salt['pillar.get'](('users:' ~ username ~ ':user_files:template'), None) -%}
 {%- set user_files_file_mode = salt['pillar.get'](('users:' ~ username ~ ':user_files:file_mode'), False) -%}
 {%- set user_files_sym_mode = salt['pillar.get'](('users:' ~ username ~ ':user_files:sym_mode'), False) -%}
+{%- set user_files_exclude_pat = salt['pillar.get'](('users:' ~ username ~ ':user_files:exclude_pat'), False) -%}
 {%- if user_files.enabled -%}
 
 {%- if user_files.source is defined -%}
     {% if user_files_sym_mode -%}
     - sym_mode: {{ user_files_sym_mode }}
     {% endif -%}
+    {% if user_files_exclude_pat -%}
+    - exclude_pat: {{ user_files_exclude_pat }}
+    {% endif -%}
     - include_empty: True
     - keep_symlinks: True
     - require: