introduction of pathlib.Path

use pathlib.Path class to specify relative paths. also added as an accepted input for the dataset classes' filepath specifier.

tests/test_dataset.py

@@ -5,8 +5,8 @@ import datetime
 import numpy as np
 import icartt
 
-# example files
-fns = pathlib.Path('./examples').glob('*.ict')
+# working directory, example files
+wd, fns = pathlib.Path('.'), pathlib.Path('./examples').glob('*.ict')
 
 def compareFiles(fn, strIn, strOut, skiplines=0, nlines=-1): # pragma: no cover
     strOut.seek(0)
@@ -63,7 +63,7 @@ def compareFiles(fn, strIn, strOut, skiplines=0, nlines=-1): # pragma: no cover
 
 class Simple1001TestCase(unittest.TestCase):
     def setUp(self):
-        self.fn         = 'tests/examples/NOx_RHBrown_20040830_R0.ict'
+        self.fn         = wd/'examples/NOx_RHBrown_20040830_R0.ict'
         self.nHeader    = 41
 
     def tearDown(self):