Prepare release 2.0.0

[d3mondev]

Entire rewrite in Go for puredns v2.0.0 release.

Additional changes:

• Stdin can be used in place of the domain list or wordlist files
• Quiet flag
• DNS load balancing handling with the --wildcard-tests flag
• Batch processing during wildcard detection with --wildcard-batch flag to help prevent memory issues that can happen on very large lists
• Progress bar during wildcard detection
• Display of options at the start of the program
• Sponsors command to view active sponsors
• More robust wildcard detection algorithm
• Remove dependency on 'pv' and do progress bar and rate limiting internally instead.
• Massdns output file is now written in -o Snl format.
• Remove default list of public resolvers
• Remove --write-answers command line option since the full wildcard answers are no longer kept in memory
• Massdns and wildcard detection will retry on SERVFAIL errors.
• Add missing entries in the massdns cache
• Many bug fixes