Handle relative URLs better, fixes #7

Created a generalized structure for waiting on unique strings

Improved duplicate URL handling

Added Go Report Card

Lint fixes

Minor corrections

Only print errors when verbose is on

Added flag for checking against a specific HTTP return code

Correct flag example

Updated README to include new flags

Added flag to only report URLs whose domain matches the initial domain, fixes #6

Avoid URLs that have already been queried, fixes #5

Remove error from NodeIter, Elements, and Anchors return tuple

Added recursive functionality, fixes #3

Move URL cleanup logic into library