background_functions is now an internal function, never called eslewhere
Macro-ised the write background part.
fixed misplaced free in transfer_free
improved style of test_loops
improved details of testing input values of w_fld
Added feature: write thermodynamics file
fixed memory leak that appeared only for isocurvature modes and no Pk
Improved testings wiht nose
added version nunber 2.1.1
added write-in-file for thermo, fixed minor bugs and improved minor stylistic details

* devel:
  added version nunber 2.1.1
  Improved testings wiht nose
  fixed memory leak that appeared only for isocurvature modes and no Pk
  Added feature: write thermodynamics file
  improved details of testing input values of w_fld
  improved style of test_loops
  fixed misplaced free in transfer_free
  Macro-ised the write background part.
  background_functions is now an internal function, never called eslewhere