Replaced ccode/regex with custom printer.
Replaced ccode/regex with custom printer.

Previously, SymPy's ccode printer was used to generate a string, and regex to
format coordinates, speeds, constants, and specifieds for Cython output.

Now, a custom ccode printer (extending current SymPy printer) outputs the
properly formatted string.

oliverlee/pydy,Shekharrajak/pydy,oliverlee/pydy,jcrist/pydy,jcrist/pydy,skidzo/pydy,jcrist/pydy,Shekharrajak/pydy,pydy/pydy-code-gen,skidzo/pydy,jcrist/pydy,skidzo/pydy,pydy/pydy-code-gen,Shekharrajak/pydy,jcrist/pydy,skidzo/pydy,jcrist/pydy,jcrist/pydy,oliverlee/pydy,Shekharrajak/pydy