zip: Made ZipBundle private, and created tests

Made ZipBundle private to simplify API (only two Zip-Funcs), and
added tests to check functionality of zipBundle. Also moved interface
"tests" to zip_test.go so not part of compile or final package.
Updated .gitignore: ignore .DS_Store (Mac OS X)
v2: Updated OpenZip, and OpenZipReader documentation.

Mentioned that Zip files opened as bundles support the Bundle,
Searcher, and Lister interfaces.
v2: updated comment about ExecutablePath() to include bug info.
v2: Added new error types, updated ErrNotFound to match, and added a function to check paths and return apropriate errors.
v2: updated to use new errors
v2: Added file system bundles.
v2: Added package bundles.
v2: added autobundles, and updated default sequence, and errors.
Merge branch 'master' of https://github.com/cookieo9/resources-go
resources/v2: added common errors
resources/v2: used common errors, and made better defaults.
resources/v2: added test zip-data.