run travis in containers!

Travis CI's container based infra allows faster builds as it allows
caching, here change is made to use wheels and cache them so that
downloads do not hit the network once cached. Though the first build
takes a bit of time, subsequent builds should be effectively able to use
the build cache and do faster builds

It breaks pkgsrc. We should move tests/ into astor/ when we have a
proper test suite.

See #3 for details.

Closes #4.

See #12.

Closes #12.

NameConstant node was introduced in Python 3.4 for True, False & None
values. This fixes #10

This commit adds a standard .gitignore for python projects primarily
ignoring Distribution/packaging files doc build files (which for this
repo might be needed in future) etc.