Assertion failure when using the `--format binary` option

[Ultrasanic]

Steps to reproduce

1. Generating a lower distance matrix in binary format
   Create a file gen.py with the following content, then run it in a virtual environment where NumPy is installed:

   import numpy as np
   
   arr = np.array([1, 1, 1], dtype=np.float32)
   arr.tofile('data.bin')

   python3 gen.py

2. Compiling Ripser
   Compile Ripser with the following flags:

   c++ ripser.cpp -o ripser -std=c++11

3. Run the program

   ./ripser --format binary data.bin

4. Observe that the program crashes with the following assertion failure:

   ripser: ripser.cpp:223: compressed_distance_matrix<Layout>::compressed_distance_matrix(std::vector<float>&&) [with compressed_matrix_layout Layout = LOWER_TRIANGULAR]: Assertion `distances.size() == size() * (size() - 1) / 2' failed.
   

[Ultrasanic]

I have submitted PR #52 to fix this issue. Waiting for review.

[Ultrasanic]

@ubauer Hi! I found a bug in read_binary() that causes an extra element to be added to distances.
PR #52 fixes the issue. Could you take a look when you have time? Thanks!