1.7.11 Issue 263, replae cat() messages in rarefy_even_depth with message()

https://github.com/joey711/phyloseq/issues/263
1.7.11 Issue 275, check/warning for empty igraph objects

https://github.com/joey711/phyloseq/issues/275
1.7.11 Remove unexpected coercion of character to factor in phyloseq:::reconcile_categories()
1.7.11 update reconcile_categories internal doc
1.7.11 Added import of igraph::vcount to the phyloseq namespace
1.7.11 additional bug fixes, deprecated function test
Merge branch 'issues-263and275'