Bugfix: incompatible character encodings

I used template for my report with Russian symbols

Error:
incompatible character encodings: ASCII-8BIT and UTF-8

Framework trace part:
….docx_replace/lib/docx_replace.rb:17:in `gsub!'
…/docx_replace/lib/docx_replace.rb:17:in `replace'
no implicit conversion of Fixnum into String

bugfix: «no implicit conversion of Fixnum  into String»
also works on dates
Merge pull request #5 from ilyario/master

Bugfix: incompatible character encodings