Port procrustes module

Ports the procrustes module, along with the tests and improved
documentation that's compliant with @jrrideout's annoying guidelines.
Refactor of Trie class
Adding documentation
Merge branch 'master' of git://github.com/biocore/bipy into port-procrustes
Fix imports and move to skbio
Move procrustes to maths.stats.spatial
Finally, nuke all occurrences of bipy
Adding tests
Adding fasta_to_pairlist functionality
Fixing Yoshiki's bug
Addressing @wasade's comments and solving merge conflicts
Merge branch 'master' of https://github.com/biocore/bipy into trie
Fixing documentation issues
Address comments by @wasade
Add brobsessive suggestions by @ElBrogrammer
Merge branch 'master' of git://github.com/biocore/bipy into port-procrustes

Conflicts:
	doc/source/index.rst
Merge pull request #151 from ElDeveloper/port-procrustes

Port procrustes module
Update .gitignore to ignore the generated folder

This folder is created when the documentation is built and pollutes the
output of git status.
Merge pull request #157 from josenavas/trie

Port Trie object to scikit-bio
Merge branch 'master' of github.com:biocore/bipy

Conflicts:
	skbio/core/tests/test_workflow.py
	skbio/core/workflow.py