flet should be cl-flet (?)

[holtzermann17]

https://github.com/vic/color-theme-buffer-local/blob/master/color-theme-buffer-local.el#L147

Otherwise, I get these errors when compiling:

In load-theme-buffer-local:
load-theme-buffer-local.el:97:54:Warning: ‘(custom-theme-recalc-face (symbol)
    (custom-theme-buffer-local-recalc-face symbol buffer))’ is a malformed
    function
load-theme-buffer-local.el:101:11:Warning: custom-theme-recalc-variable called
    with 2 arguments, but accepts only 1
load-theme-buffer-local.el:102:21:Warning: reference to free variable ‘symbol’

In end of data:
load-theme-buffer-local.el:109:1:Warning: the following functions are not
    known to be defined: flet, symbol

[nivekuil]

The currently open PR has the right idea using noflet. cl-flet has different behavior that will set the theme for the whole session