Rearrange the assignment of self.gpghome to go before self.gpgbinary.
Rewrote more unittests. All basic tests now pass.
Change assert to check for bytearray stream rather than file handle.
Fix error where unpermitted variables would remain on a heap.
Modify logic for creating path to secret keyring.
Change keyring file specification options.

 * Add DeprecationWarning for gnupg.GPG.keyring parameter, and first steps
   towards moving to use gnupg.GPG.secring and pubring instead, because
   'keyring' seemed unclear as to which keyring it was referring to.
 * Add checks for keyring files, and create them if they are not there.
 * Update documentation for gnupg.GPG.__init__().
General code cleanup.

 * Move exceptions and global parameters to top of file.
 * Move global function to top of file before classes and alphabetise them.
Shorten code for setting keyring paths.
Add module name in order to register it in test_gnupg.py.
Fix a bug where gpg status message handling did not work for signatures.

 * If an attempt was made to check a signature and none was found, the
   status message would not get handled.
Fix a bug where the unittests were leaving hanging file descriptors.

 * The old unittests did not clean up temp files properly in some test cases.
Clean up a few import statements.
Change debugging messages for key import tests to be more precise.

 * Also, disabled doctest runs when called with "$ python test_gnupg.py".