table->rows function in cucumber-clojure allows spaces in keys

[mpkorstanje]

From: cucumber/cucumber-jvm#752

It is very common to write a table with a column named with spaces (e.g. 'address line 1'), however having spaces in keywords in clojure makes life harder that it should. I know specflow strips spaces (it also ignore case) of tables when the developer wants to read it, so I would like to propose to do the same here (or replace by dashes - which I'm more tempted). I don't mind making a pull request with this change, but before spending some cycles on it, I want to know if 1) this change would be accepted and 2) if should strip the spaces or add dashes.