CLN: remove engine detection and manip for datetimes
CLN/ENH: encapsulate Terms and Constants
ENH: allow an already-parsed expression to be passed to eval
CLN: add automatic scope creating object
CLN: make the environment an implementation detail
DOC: add docstring to eval
CLN: have the Scope instance auto create the scope if none exists
CLN: add six.string_types checking instead of basestring
CLN: use shiny new string mixin to refactor repring
CLN: move align to its own file
CLN: use new stringmixin for Expr base class
ENH/CLN: be more careful about unicode
DOC: reference future enhancingperf.eval section
API: expose the computation.expr.Expr object to top level pandas
CLN/TST: fail with a NotImplementedError on Python boolean operators
CLN: generlize operator/expression printing
ENH: add modest type inference
ENH: rewrite assignment as equal comparison
ENH: initial commit for adding Expr based terms for pytables support
WIP: still some debugging statements in