Decode

- Remove joke functions
- Use Travis CI to do auto testing and docs building
- Docs are now hosted in the `gh-pages` branch

+ `plot_chmap` now returns mappable and does not plot colorbar inside it
+ Delete default styles of xlabel, ylabel, and title of plot functions
+ Fix `plot_timestream` (before that an error occurs when plotting)

Removed
+ `dc.models.skewgauss()`
+ `dc.models.r_subtraction()`
+ `dc.models.savgol_filter()`
+ `dc.models.rsky_calibration()`
+ `dc.plot.plotweather()`

Implemented
+ `dc.models.gauss_fit()` made by Koyo
+ `dc.fromcube()` made by Akio
+ `dc.plot.plot_chmap()` made by Tsuyoshi

Updated
+ `plotcoords()` => `plot_tcoords()` (backward compatibility has been held)
+ `plottimestream()` => `plot_timestream()` (**backward compatibility has been lost**)
+ `plotspectrum()` => `plot_spectrum()` (backward compatibility has been held)
+ `savefits()`
- casaviewer has been supported
- still should be upgraded

Miscellaneous
+ implemented `deprecation_warning` decorator
+ changed some of the internal structures
+ made the logger fucntions a standard way

This release fixed the following bugs:

1. [creation of default scantype](https://github.com/deshima-dev/decode/commit/953bd5ac749803cd4033f3b85e5c4c3a4fd2d84c)
2. [invalid function name](https://github.com/deshima-dev/decode/commit/f37ef88197679bcac56e05a3d3fb2a6fac0e0495)

array function
dc.concat
+ [**Bug Fixed**] `xref` and `yref` of the concatenated array is adjusted to the 1st array.

i/o function
dc.io.loaddfits
+ A new keyword of `shuttle` is implemented for shuttle observations. When this is True, x coordinates of off-point and on-point are specified via keywords of `xmin_off`, `xmax_off`, `xmin_on`, and `xmax_on`.

model funtion
+ **Calculation speed gets much faster!**
dc.models.chopper_calibration
+ A new calibration method has been implemented. This can be used in the same way as dc.models.rsky_calibration.
python
dc.models.chopper_calibration(onarray, offarray, rarray, Tamb, mode='mean')