resource(".xls") -> Excel

adds into(DataFrame, Excel) using pd.read_excel
Merge branch 'master' into resource_excel

Refactor resource(Excel) for new regex technique
add into(DataFrame, Excel) tests in test_into.py

Conflicts:
	blaze/api/into.py
	blaze/api/resource.py
	blaze/api/tests/test_resource.py
	blaze/data/__init__.py
Add unbiased to std and var reduction expressions
bcolz unbiased std/var
numpy unbiased std/var
pandas unbiased std/var
python unbiased std/var
Add documentation to clarify unbiased
Adding Coveralls
Added blank line
Added setup.cfg file for arguments.
Added new coverage method to .travis.yaml.
switching in valid 26 python detection statement
Merge pull request #583 from quasiben/feature/binstar_ci

Proper 26 Building
Use fixtures and clean up skipping based on lack of connection
Add summary test
Implement Summary for mongo
Merge pull request #544 from cpcloud/add-unbiased-option

Add unbiased option to std and var expressions
Only connect and setup once
Give reasons for failing