introduce Noise/Budget .run() method to simplify basic usage

Should cover/simplify the most common use case, equivalent to running:

load()
update(**kwargs)
calc_traces

README.md

@@ -18,7 +18,7 @@ description is loaded, the noise budget can be calculated and plotted:
 >>> freq = np.logspace(1, 3, 1000)
 >>> Budget = gwinc.load_budget('aLIGO')
 >>> ifo = gwinc.precompIFO(freq, Budget.ifo)
->>> traces = Budget(freq, ifo=ifo).calc_trace()
+>>> traces = Budget(freq, ifo=ifo).run()
 >>> fig = gwinc.plot_noise(freq, traces)
 >>> fig.show()
 ```

gwinc/__init__.py

@@ -113,7 +113,7 @@ def gwinc(freq, ifo, source=None, plot=False, PRfixed=True):
     # from just ifo description, without having to specify full budget
     Budget = load_budget('aLIGO')
     ifo = precompIFO(freq, ifo, PRfixed)
-    traces = Budget(freq, ifo=ifo).calc_trace()
+    traces = Budget(freq, ifo=ifo).run()
     plot_style = getattr(Budget, 'plot_style', {})
 
     # construct matgwinc-compatible noises structure

gwinc/__main__.py

@@ -179,10 +179,7 @@ def main():
             logging.info("precomputing ifo...")
             ifo = precompIFO(freq, ifo)
         logging.info("calculating budget...")
-        budget = Budget(freq=freq, ifo=ifo)
-        budget.load()
-        budget.update()
-        traces = budget.calc_trace()
+        traces = Budget(freq=freq, ifo=ifo).run()
 
     # logging.info('recycling factor: {: >0.3f}'.format(ifo.gwinc.prfactor))
     # logging.info('BS power:         {: >0.3f} W'.format(ifo.gwinc.pbs))

gwinc/nb.py

@@ -32,7 +32,7 @@ class BudgetItem:
         return None
 
     def update(self, **kwargs):
-        """Overload method for updating data needed to calculate final PSD.
+        """Overload method for updating data.
 
         By default any keyword arguments provided are written directly
         as attribute variables (as with __init__).
@@ -42,7 +42,7 @@ class BudgetItem:
             setattr(self, key, val)
 
     def calc(self):
-        """Overload method for calculation of final PSD.
+        """Overload method for final PSD calculation.
 
         Should return an array of power-referenced values evaluated at
         all evaluation frequencies (self.freq).
@@ -152,6 +152,17 @@ class Noise(BudgetItem):
             data = None
         return data, self.style
 
+    def run(self, **kwargs):
+        """Convenience method to load, update, and return calc traces.
+
+        Equivalent of load(), update(), calc_traces() run in sequence.
+        Keyword arguments are passed to update().
+
+        """
+        self.load()
+        self.update(**kwargs)
+        return self.calc_trace()
+
 
 class Budget(Noise):
     """GWINC Budget class