Hotfix/readfile

This is to fix an `Undefined subroutine &WeBWorK::PG::Translator::fileFromPath` error that occurs on perl 5.18 (at least).    I have tested on 5.12 and 5.18 with success.

It also includes a .gitignore to handle the generated lib/chromatic/color file that is generated.  

To test, try on other perl versions that this error isn't generated when viewing a problem. 
I'm a little concerned that the setting of `@export` is no longer in a `BEGIN` block, while the use of it (line 38 below) *is* in a `BEGIN` block.  I'm wondering if the value for `@export` will be empty at line 38 (since that should run before non-`BEGIN` code).