Log Message:
math/ruby-spreadsheet: update to 1.1.7
### 1.1.7 / 15.03.2018

commit 34ece5f4e7ab2907c4a8809d96ef2a33b7ccd4b5
Author: Maarten Brouwers <github@murb.nl>
Date:   Thu Mar 15 15:10:23 2018 +0100

* shadowing outer local variable - i

* Running rake resulted in the following warning: \ 
`lib/spreadsheet/worksheet.rb:345: warning: shadowing outer local variable - i`; \ 
this patch fixes that.