Added merge, join, groupby, hierarchical indexing to 03-data, updated readmes

Author: gregparkes

.gitignore

@@ -1,2 +1,3 @@
 *.ipynb_checkpoints
-*.Rhistory
+*.Rhistory
+__pycache__

01-Principles/README.md

@@ -11,6 +11,10 @@ Internal packages we draw on include:
 3. `os`
 4. `sys`
 
+Prerequisites:
+
+1. NONE
+
 ## Basics of Python
 
 In the first section, you will cover:

02-Simulation/README.md

@@ -12,6 +12,11 @@ Requirements:
 4. `matplotlib`
 5. Other performance libraries (optional); `cython`, `numba`
 
+Prerequisites:
+
+1. Basic level of Python
+2. `itertools`
+
 ## Basics to NumPy
 
 **NumPy** is a core library package for scientific computing in Python, whereby it provides a high-performance multi-dimensional array/matrix object, written in C with a Python header, and a host of functions for array creation, access, manipulation and deletion. For example arrays are created as: