build uses 2 jobs on travis
Merge pull request #474 from Garonenur/travis

build uses 2 jobs on travis
Register for GtGFF3OutStream class
Fixing prototype defs
Registering prototypes for node stream and GFF3 visitor
Registering more prototypes
Finished review of extended/
Finished review of core/
For some reason my text editor is changing file permissions of Python files; changing back
Let's see if gt_sort_stream can solve our problems
Minor fix
Replaced Python wrapper classes with c_void_p in argtypes and restype declarations for several classes, enough for a minimal example to work correctly on OS X
Fix issues with `gt/extended`

The _as_parameter_ / from_param() mechanism from Python's ctype module does not appear to work correctly on Mac OS X.
This commit adjusts C library calls and function prototype definitions do that they explicitly reference pointers to
C objects (rather than their Python wrappers).
Alphabetized
Fix ctypes issues with
Use ._as_parameter instead of .from_param()
Minor fix
gtpython: more cleanups/fixes for Mac OS X ctypes
optionally allow non-unique ID output in GFF3 visitor
gtlua: add gt_lua_genome_visitor_push()