Bump NPM version to 0.5.4 in preparation for publishing.
Merge pull request #67 from briandipalma/master

Implement NodePath.prototype.prune.
Bump NPM version to 0.5.5 in preparation for publishing.
feat(NodePath.prune): deal with an IfStatement not having its consequent after a prune.

If an IfStatement has it's consequent pruned and there is no alternate leave the test as
a ExpressionStatement. If the alternate still exists negate the test and move the alternate
to the consequent position.