Gwpy

The 4th beta release of GWpy 0.1, mainly just to provide a more up-to-date tarball for users.

Bug-fix for 0.1b2 to fix build error with detached HEAD used by travis-ci.org

Second beta release

Main focus:
- `gwpy.data.Array` now inherits directly from `astropy.units.Quantity`
- moved old `timeseries.common` methods upstream into `Series` class
- reworked `TimeSeries` reading from GWF with multi-channel LALFrame hooks, and generic interface between `framecpp` and `lalframe`
- numerous optimisations, new tests, and documentation updates

First beta release
- bug fixes all over the place from last alpha
- new command-line interface with `gwpy-plot` script