Getopt

[yonatanzunger]

Updates for issue https://github.com/aichingm/rfc2epub/issues/6 .

• Change option parsing to use getopt
• Add options for font size, preserving page breaks
• Add --preset option to set optimal defaults for given devices

[yonatanzunger]

(Hold on one sec, something seems to have broken if you use a custom font and turn off page break preservation -- fixing)

[yonatanzunger]

(OK, now it works and is ready for review)

[aichingm]

Thanks for your contribution!