*  command line options

*  postscript/gif/other export

*  fix equation intercept solving algorithm, it doesn't solve equations that
   touch, but don't cross, eg f(x) = sin(x) and f(x) = 1

*  fix the bug in parsing ^ (power). Explicit bracketing is necessary
   to parse correctly. For example, f(x) = x * 2 ^ x is parsed incorrectly,
   need to write x * (2 ^ x)
