Fixed point missing initialisation

Fixed missing initialisation for point Boolean variable to False

Single point workflow

Functions will try to determine if there's only one dimension (time) and accordingly skip all the grid based operations, as land_check and parallel loops. This release should solve issue #56

Updated requirements

Updated requirements.txt file to remove pin for xarray

Removed multi index

As described in pull -request #53 some changes in the way coordinates are handled following changes in indexing in the latest xarray release, see also issue #49

Conda and docs fixed

Changes to conda files and a few changes to the documentation. The code isn't changed at all compared to 0.8.0 and this version won't be published, I need a release to create the documentation

Added timestep option

Main updates:
Added a tstep (timestep) option to use the original timestep of the timeseries passed as input as step, rather than assuming data is daily. This allows to calculate climatologies and detect mhw events at different frequency.
Added conda support
Added readthedocs documentation

Improved threshold and documents

Main improvements are:
Re-organised threshold function - now the calculation of percentile and average are separated in delayed functions.
Added options to handle NaNs, in particular to be able to use mean() and quantile() function without skipna=True by default.
Update xmhw_demo notebook and documentation to reflect changes.
Removed bug from stats and added tests.

First release

The tool is currently reproducing Eric Olivier code to calculate threshold, identify marine heatwave events and calculate some of the block averages.