Bye Bye ASCAT readers and small bugfixes.

• Moved the ASCAT readers to the ascat package. The functionality is the same, just replace
  import pytesmo.io.sat.ascat by import ascat and everything should work the same as before.
• The H07 reader now returns also ssm mean as a value between 0 and 100. Before
  it was between 0 and 1 and inconsistent with the other ssm values.
• Fix small bug in julian date calculation and add tests for it.
• Add hamming window to resample module