Move ForceBalanceBaseClass and BaseReader to __init__

Since ForceBalanceBaseClass and BaseReader are needed by a number of other
forcebalance classes but don't do anything themselves, they can be moved
to __init__ as forcebalance.BaseClass and forcebalance.BaseReader. This is
more in line with standard python programming practices and consolidates
common classes used across the forcebalance package into one place.
Adjust module imports for consistency
Merge branch 'master' into base_into_init

Merge in changes from switch to logging module so that
base_to_init can be merged back into master

Conflicts:
	src/forcefield.py
	src/optimizer.py
Merge branch 'master' into base_into_init

Conflicts:
	src/optimizer.py
Merge branch 'master' into base_into_init
Merge pull request #5 from leeping/base_into_init

Move ForceBalanceBaseClass and BaseReader to __init__