Add splash screen elements

Add a table at the top of the document that holds the logo for emperor
in it. This table is hidden once the metadata-mapping file and
coordinates javascript objects are loaded.

Fixes #33
Add favicon to index.html

Logos are of course original creations of @meganap
Merge pull request #77 from ElDeveloper/issue_33

As the code works well and the build was successful I'm going to merge the PR.
Merge branch 'master' of git://github.com/qiime/emperor into issue_6
Update test for case with vectors

This test was failing because another branch was merged into the master
branch before this one.
Fix bug where --color_by would exclude items

When selecting only field A wit --color_by and then trying to add
vectors using field B and C the script would fail to recognize fields B
and C and exclude them from the analysis. Thanks for catching this issue
@antgonza.

A new enhacement has been added, now you can concatenate columns on the
mapping file using && for --add_vectors field.