Refactor

- **Breaking API changes**
 -- Removed methods: `run`, `call`, `lookfor`
 -- Renamed methods: `_eval` -> `eval`, `get` -> `pull`, `put` -> `push`,
    `close` -> `exit`
 -- Removed run and call in favor of using eval dynamic functions.
 -- Renamed methods to avoid overshadowing Octave builtins and for clarity.
 -- When a command results in "ans", the value of "ans" is returned
    instead of the printed string.
- Syntax Errors on Windows no longer crash the session.
- Added ability to interrupt commands with CTRL+C.
- Fixed Octavemagic not following current IPython working directory.
- Dropped support for Python 2.6.