improvements to plot formatting

...del_dg_var_tags_transposedelems_NVIDIA_C2070_xylabels.pdf

...l_dg_var_tags_transposedelems_NVIDIA_GEFORCE_nolabels.pdf

...odel_dg_var_tags_transposedelems_NVIDIA_K40C_nolabels.pdf

...t_demo_linear_model_fd_var_tags_NVIDIA_C2070_xylabels.pdf

...demo_linear_model_fd_var_tags_NVIDIA_GEFORCE_nolabels.pdf

...ot_demo_linear_model_fd_var_tags_NVIDIA_K40C_nolabels.pdf

...t_demo_nonlin_model_mm_var_tags_NVIDIA_C2070_xylabels.pdf

...demo_nonlin_model_mm_var_tags_NVIDIA_GEFORCE_nolabels.pdf

...ot_demo_nonlin_model_mm_var_tags_NVIDIA_K40C_nolabels.pdf

.../plot_demo_nonlin_model_overlap_NVIDIA_C2070_xylabels.pdf

...lot_demo_nonlin_model_overlap_NVIDIA_GEFORCE_nolabels.pdf

...a/plot_demo_nonlin_model_overlap_NVIDIA_K40C_nolabels.pdf

examples/make_demo_plots.py

perflex/evaluation.py