fix bug with OptionsPattern[]
Partition doc fix: add </dl>
Add Depth[]
Add Operate[]
Add Through[]
Add IntegerDigits[]
Add a basic version of Variables[]

This is a start, but it could do with more work. It feels like
something SymPy could do, but I didn't find a function for it.
Add Complement[]
Add an example of IntegerDigits[n] with n < 0
add missing blank line
Merge pull request #137 from sn6uv/OptionsPattern

fix OptionsPattern[] bug
Simplify Operate by using get_int_value() instead of to_python()

get_int_value() handles conversion to Python and checking that the
input is the proper type. This means we only need one pattern.
Operate: improve message and add test case for n < 0
Use SymPy to improve Variables

This makes it match the first few examples in the Mathematica docs,
but it's still not complete. Add a note about this.
Merge pull request #148 from bnjones/mma-funcs

Add some structure-related functions
disable Travis benchmarks
Fix line numbering in the command-line shell

The code that handled the terminal prompt was treating $Line as the
next line number. This meant that $Line and In/Out were off by one:

  In[1]:= $Line
  Out[1]= 2

Fix this by treating $Line as the last line number when handling the
prompt.
Fix broken line wrapping with readline and coloured prompts

Readline needs to know the width of the prompt in order to wrap lines
correctly. To get this right, it has to know which character sequences
don't take up any screen space. The \001 and \002 characters (ASCII
SOH and STX) indicate the beginning and end of a nonprinting character
sequence.

Fix the line wrapping by surrounding any colour escapes with these
characters.