added roi, noise and gain (#143)

- Moved definitions of Cluster_2x2 and Cluster_3x3 to it's own file
- Added optional members for ROI, noise_map and gain_map in ClusterFile

**API:**

After creating the ClusterFile the user can set one or all of: roi,
noise_map, gain_map

```python
f = ClusterFile(fname)
f.set_roi(roi) #aare.ROI
f.set_noise_map(noise_map) #numpy array
f.set_gain_map(gain_map) #numpy array
```

**When reading clusters they are evaluated in the order:**

1. If ROI is enabled check that the cluster is within the ROI
1. If noise_map is enabled check that the cluster meets one of the
conditions
    - Center pixel above noise
    - Highest 2x2 sum above 2x noise
    - 3x3 sum above 3x noise
1. If gain_map is set apply the gain map before returning the clusters
(not used for noise cut)

**Open questions:**
1. Check for out of bounds access in noise and gain map?

closes #139 
closes #135 
closes #90

patches/libzmq_cmake_version.patch

@@ -0,0 +1,18 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index dd3d8eb9..c0187747 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -1,11 +1,8 @@
+ # CMake build script for ZeroMQ
+ project(ZeroMQ)
+ 
+-if(${CMAKE_SYSTEM_NAME} STREQUAL Darwin)
+-  cmake_minimum_required(VERSION 3.0.2)
+-else()
+-  cmake_minimum_required(VERSION 2.8.12)
+-endif()
++cmake_minimum_required(VERSION 3.15)
++message(STATUS "Patched cmake version")
+ 
+ include(CheckIncludeFiles)
+ include(CheckCCompilerFlag)