Breaking changes from 0.3.3->0.3.4

This package works as expected when you install it through npm(v0.3.3) but when I cloned the repo and tried to run demo.js I get the following error when it tries to evaluate `$c := ...`
```
Error: no registered db info found...
at load (/Users/root/nquery/demo/loader.js:44:8)
```

The problem seems to be with the AST creation. In the newer version the AST doesn't show the tables `a` and `b` used for evaluation as 'var' type. Rolling back to the commit 395487a833d0f704a16f4a898dd9a554c94a6e76 fixed the issue.

Start by running demo.js and inspect the failure in demo/loader.js at line 44 when evaluating `$c := ...`. Compare the AST for tables `a` and `b` with the behavior at commit 395487a833d0f704a16f4a898dd9a554c94a6e76. Done means the tables are represented as `var` for evaluation and demo.js no longer reports missing database info.

Written by the indexing model from the issue text.