docs(readme.md): add quick start code snippet to readme file (#568)

* Adding a quick start code snippet to the main readme.md file.

* trying a relative path

* Further simplifying and using consistent names

README.md

@@ -30,6 +30,41 @@ FloPy code documentation is available at [http://modflowpy.github.io/flopydoc/](
 Getting Started
 -----------------------------------------------
 
+### MODFLOW 6 Quick Start
+```python
+import os
+import flopy
+ws = './mymodel'
+name = 'mymodel'
+sim = flopy.mf6.MFSimulation(sim_name=name, sim_ws=ws, exe_name='mf6')
+tdis = flopy.mf6.ModflowTdis(sim)
+ims = flopy.mf6.ModflowIms(sim)
+gwf = flopy.mf6.ModflowGwf(sim, modelname=name, save_flows=True)
+dis = flopy.mf6.ModflowGwfdis(gwf, nrow=10, ncol=10)
+ic = flopy.mf6.ModflowGwfic(gwf)
+npf = flopy.mf6.ModflowGwfnpf(gwf, save_specific_discharge=True)
+chd = flopy.mf6.ModflowGwfchd(gwf, stress_period_data=[[(0, 0, 0), 1.],
+                                                       [(0, 9, 9), 0.]])
+budget_file = name + '.bud'
+head_file = name + '.hds'
+oc = flopy.mf6.ModflowGwfoc(gwf,
+                            budget_filerecord=budget_file,
+                            head_filerecord=head_file,
+                            saverecord=[('HEAD', 'ALL'), ('BUDGET', 'ALL')])
+sim.write_simulation()
+sim.run_simulation()
+head = flopy.utils.HeadFile(os.path.join(ws, head_file)).get_data()
+bud = flopy.utils.CellBudgetFile(os.path.join(ws, budget_file),
+                                 precision='double')
+spdis = bud.get_data(text='DATA-SPDIS')[0]
+pmv = flopy.plot.PlotMapView(gwf)
+pmv.plot_array(head)
+pmv.plot_grid(colors='white')
+pmv.contour_array(head, levels=[.2, .4, .6, .8], linewidths=3.)
+pmv.plot_specific_discharge(spdis, color='white')
+```
+<img src="examples/images/quickstart.png" alt="plot" style="width:30;height:30">
+
 ### [Frequently asked questions](docs/flopyFAQ.md)
 
 ### [Tutorials](http://modflowpy.github.io/flopydoc/tutorials.html)