Moved python project into etaetaprime package
Updated docs to conform to new package layout.
Added more detail to fileio docstrings.
Added return type to read2pt function docstring.
Updated gitignore
Added init to etaetaprime package.
Added some basic tests of existing functions that use py.test.
Added correlators module to calculate correlators from traces.
Added efficient cython function to do outer subtraction of two arrays
Added optimized diff function into combine traces function.