add support for dependency tree rendering

[ghost]

adds support for printing the dependency tree of a package, by directly using the function and package(archy), that bower itself uses.

current output

Running "bower:list" (bower) task
check-new >> Checking for new versions of the project dependencies..
>> dependency tree:
bower-demo#1.0.0
├── JSON-js#3d7767b6b1
└── jquery#1.7.2 incompatible with ~2.1.3 (2.1.3 available)

>> Bower command finished.

Done, without errors.

[coveralls]

Coverage decreased (-12.52%) to 31.48% when pulling fd805e6 on suyashv:add-dependency-tree-rendering into 542bb12 on dherges:master.

[coveralls]

Coverage decreased (-12.52%) to 31.48% when pulling fd805e6 on suyashv:add-dependency-tree-rendering into 542bb12 on dherges:master.

[dherges]

Thanks! Merged into master and published a new version 0.3.1 to npm registry.