Basic HTML Table to reStructuredText Support for HTML2RST service on GAE Go

Add basic HTML table to reStructuredText support for online HTML to reStructuredText service on Google App Engine Go. Based on my previous work [1] and [2].

Online HTML to reStructuredText

For HTML table to reStructuredText implementation, see this commit. For complete source code, source code, see GitHub html2rst repo.

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Tested on: Ubuntu Linux 16.04, Google App Engine SDK for Go 1.9.37.

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References:

[1]	[Golang] Unrobust HTML Table to reStructuredText list-table

[2]	Online HTML to reStructuredText on Google App Engine Go

[3]	[Golang] Convert File Encoding From Big5 to UTF-8

[4]	[Golang] HTML to reStructuredText