Check reading from a PDB functionality

[tlfobe]

We would like to be able to load in structures from a pdb from other programs (cg_openm, foldamers, etc.). Using pyrosetta.pose_from_pdb() we should be able to read in structures into PyRosetta.

[tlfobe]

Update to this issue:

I am able to read in PDB files with CG11x3 models. Energy outputs are similar, but not exactly the same. I believe this has to do with the truncation done in writing PDBs. Looking into high precision ways to write files in Rosetta.

Output of assert_almost_equal for energies between an original pose and that same pose being read in from pose_from_pdb.

Arrays are not almost equal to 7 decimals
 ACTUAL: -3.1096148301871103
 DESIRED: -3.1154496225609503

[tlfobe]

Moved this into a functional test as per issue #13 , see commit 1a0f005

[tlfobe]

Due to the precision output, the differences between read-in and simulated structures is expected. If we need to high precision output files for reading into other programs, we should be able to adjust Rosetta's output precision.