poppr version 2.2.1

This is mainly a maintenance release. One major change is the poppr manual being converted to HTML. Some sections were removed.

BUG FIX

• A problem exporting haploid sequence data to genalex format was fixed
  (see #108)
• Data without population structure no longer throws an error in imsn()

NEW FEATURES

• You can now specify layout parameters in imsn()
• The *.msn functions will now take into account whether or not your data is set
  to collapsed MLGs. (see #107)

MISC

• Errors from mlg.filter now make more sense.
  (see #109)
• The vignette poppr_manual has been converted to HTML format.
  (see #113)