Add base16-solarized theme

This theme is a 256 color variant and it uses the color
codes of the base16-solarized (256 color) terminal/shell theme:
https://github.com/chriskempson/base16
https://github.com/chriskempson/base16-shell

It is based on the original tmux-colors-solarized light theme with some
color codes changed (to map solarized base2, base00, orange, base1).

In fact, this theme may be used in combination with any base16 256 color
terminal/shell theme. But it will probably look a bit 'burnt' (i.e.
solarized).  It better matches the base16-solarized-light and
base16-solarized-dark terminal/shell color themes.

Author: mshkrebtan

tmuxcolors-base16.conf

@@ -0,0 +1,34 @@
+#### COLOUR (base16-solarized)
+
+# default statusbar colors
+set-option -g status-bg colour18 #base2
+set-option -g status-fg yellow #yellow
+set-option -g status-attr default
+
+# default window title colors
+set-window-option -g window-status-fg colour20 #base00
+set-window-option -g window-status-bg default
+#set-window-option -g window-status-attr dim
+
+# active window title colors
+set-window-option -g window-status-current-fg colour16 #orange
+set-window-option -g window-status-current-bg default
+#set-window-option -g window-status-current-attr bright
+
+# pane border
+set-option -g pane-border-fg colour18 #base2
+set-option -g pane-active-border-fg colour19 #base1
+
+# message text
+set-option -g message-bg colour18 #base2
+set-option -g message-fg colour16 #orange
+
+# pane number display
+set-option -g display-panes-active-colour blue #blue
+set-option -g display-panes-colour colour16 #orange
+
+# clock
+set-window-option -g clock-mode-colour green #green
+
+# bell
+set-window-option -g window-status-bell-style fg=colour18,bg=red #base2, red