Error parsing tabbed empty lines

[soggie]

When using an IDE to write feature files, the IDE automatically inserts indentation to every empty lines. However, in kyuri, this causes it to fail on an OUTDENT error. Easiest way to reproduce this bug is to write this:

Scenario: A positive control test
    GIVEN the string "Elcomeway otay Arkfay Owntay"
    THEN the stat's string output should show: 4/4 [100%]
    <-- put a tab here
Scenario: A negative control test
    GIVEN the string "Welcome to Fark Town"
    THEN the stat's string output should show: 0/4 [0%]

This would cause the kyuri compiler to fail. What it should actually do is when parsing tabs, if the following line is empty, ignore it rather than crash.

We're putting this fix into our own fork (rajkissu), and will be submitting a pull request soon which also contains bug fixes for a couple other bugs (AND keyword as well as tabs-as-spaces bug).