v1.3.11 Added tree option for import_biom()

phyloseq 1.3.11
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- Added tree option for import_biom() importer so that users can avoid
  using merge_phyloseq() if their files are otherwise standard vanilla
- Address Issue 169 and 167
https://github.com/joey711/phyloseq/issues/169
https://github.com/joey711/phyloseq/issues/167