Corrected bug with looking for excitation file in same directory as input file.

docs/source/input.rst

@@ -666,7 +666,7 @@ If there are less amplitude values than the number of iterations that are going
 
     #excitation_file: file1
 
-``str1`` is the name of the ASCII file containing the specified waveform. It should be located in the same directory as the input file.
+``str1`` is the name (and optionally full path) of the ASCII file containing the specified waveform. ``str1`` will first be tested as the full path to the file, and if it does not exist it will look for ``str1`` in the same directory as the input file.
 
 For example, to specify the file ``my_waves.txt``, which contains two custom waveform shapes, use: ``#excitation_file: my_waves.txt``. The contents of the file ``my_waves.txt`` would take the form: