Is null properly evauluates undefined variable pursuant to #140
Longs are now evaluated at face-value per #142
Combined MapLoopControl and LoopControl into For, reducing duplication and matching with the tag name anyway. Pursuant to #134, we now evaluate the else tag in the for loop.
Merge branch 'is-null-fix' of github-personal:thomas-p-wilson/jtwig
Merge branch 'for-else-evaluation' of github-personal:thomas-p-wilson/jtwig