merge source comments; ignore private functions

Merge comments found in the source file with those generated by
    smartcomments - give preference to the source file's comments where
    there are collisions

Provide an option in the config file to ignore private functions
    (any function with a name that starts with '_').  Private functions
    are ignored by default.

rename bin/index.js to bin/smartcomments
better merge logic; misc other
fix in mergeOtherSrcTags()

fix in mergeOtherSrcTags()
add a few comments
added config option favor_generated for @return

added a config option favor_generated - if true (the default), the
    generated comment's @return tag (and possibly other tags in the
    future) overrides what is in the source file.  Otherwise, the source
    file @return or @returns tag is kept.  The reason one might want to
    keep the source file's @return is that it might have additional
    description about what is being returned beyond just the type.