No more precomp

This finally gets rid of the whole precompIFO function. It does this by breaking up precomp into various smaller functions, moving them into the common IFO noise definition module, and using them appropriately when needed. This does result in some of the functions being called multiple times in the full budget calculation for the aLIGO-like budgets, but the cost should be minor given the convenience of getting rid of the whole precomp thing, thereby opening up everything to non-aLIGO-like configurations.

Even though some functions are calculated multiple times, we're still orders of magnitude faster than matgwinc, so... Should still revisit down the line though.

closes #40 (closed)

gwinc/io.py

-import datetime
 import h5py
+import datetime
 
 
 SCHEMA = 'GWINC noise budget'
@@ -42,7 +42,7 @@ def _read_trace_recursive(element):
         if isinstance(item, h5py.Group):
             trace[name] = _read_trace_recursive(item)
         else:
-            trace[name] = item.value, dict(item.attrs.items())
+            trace[name] = item[:], dict(item.attrs.items())
     return trace
 
 
@@ -54,7 +54,7 @@ def load_hdf5(path):
     """
     with h5py.File(path, 'r') as f:
         # FIXME: check SCHEMA name/version
-        freq = f['Freq'].value
+        freq = f['Freq'][:]
         traces = _read_trace_recursive(f['/traces'])
         attrs = dict(f.attrs.items())
         return freq, traces, attrs