Filterbank and Frequencies

* Frequencies, EqualBand and OctaveBand for describing frequency bands.
* Filterbank for filtering a signal with any of the above frequency band
containers
Merge pull request #57 from FRidh/filterbank2

Filterbank and Frequencies
Add ISO/TR 25417 quantities
Merge pull request #58 from FRidh/iso25417

Add ISO/TR 25417 quantities
Absolute imports
Merge pull request #59 from felipeacsi/abs-import

Absolute imports
Cleaning code
Merge pull request #60 from felipeacsi/cleaning

Cleaning code
Quantities and Units
Merge pull request #61 from FRidh/quantities

Quantities and Units
Docs ISO 25417
IEC 61672

Nominal frequencies and weighting filters.

Yes, you see that right. There is an array of just zeros :-)

More to come...
Merge pull request #62 from FRidh/standard

IEC 61672 and doc updates to ISO 25417
IEC 61672: Time-averaging and time-weighting
Merge pull request #64 from FRidh/iec

IEC 61672: Time-averaging and time-weighting
Removed unnecessary import
Merge pull request #65 from python-acoustics/import

Removed unnecessary import
Octave: properties
NEW: integrate_bands to change frequency resolution of spectrum.
Force Tox tests against scipy 0.13.3