subdivide README.md

update URLs in README.md

reformat code

Added tag 2.11 for changeset 9678f86d3f6f

add default namespaces also in XPath expressions containing "and" or "or"

fix version number

improve word order in README.md

sort options in usage list in README.md

Added tag 2.10 for changeset 1ae5775b4eab

add option "-s" ("--spaces")

add options "-p" ("--pis") and "-P" ("--comments")

simplify argument parser

remove whitespace in shebang

fix link to COPYING in README.md

change color of ellipsis in abbreviations

Added tag 2.9 for changeset 254dec1347bf

add option "-a" ("--abbreviate")

Added tag 2.8 for changeset feeb9e97dbc3

add option "-M" ("--files-and-matches")

update README.md