v2.1: mdfreader export to xlsxs avoids export of mdf4 array channels

New feature :
Warn user of unfinalised mdf4 file (from 4.11)

bug fix:
xlsx export robustness improvement regarding various kind of data
unsorted VLSD CG handling
convertToPandas bug fix for unsorted data

mdf class refactoring plus bug fixes

Major change : introduced mdf_skeleton class in mdf module in order to give flexibility of changing data structure without major impact on other modules. File metadata (date, time, author, etc.) are now accessible from file_metadata attribute. Also improved mdf representation with more concise print.
Improved memory consumption from both mdf3 and mdf4 by removing single file multiprocessing (mdfconverter still using file by file multiprocessing).
bugs fixes:

• thanks to mdf_skeleton, properly tackle unique name concern by appending datagroup number to channel name
• generally improved robustness of export methods

Cython introduction

Corrected bug for non existing units in mdf4
Added dataRead cython extension to speed up by x60 processing of non byte aligned data (could not use numpy, used bitarray module at first but too slow). As cython requires compilation, I can not test all platforms, do not hesitate to feed back in case of issues.

pip packaging

Packaging for pip has been improved in this version. After install, mdfreader can be called from ipython and mdfconverter from prompt can launched.

Modifications to make mdfreader compliant to packaging

Arranged folder structure for packaging
Arranged also folder for documentation

First complete realease of mdfreader on github

First mature pre-release of mdfreader includig mdf 4 reading (passed all tests)