Fixed bug in Predict_TLE::__construct()

* Some TLEs use leading spaces instead of zeros.  This caused
  the casting of the epoch '14 089.1234234' to '14', wreaking
  havoc on predictions.
* See http://www.celestrak.com/columns/v04n03/ for details on
  the format, and which fields may use leading spaces.
* The original code this was ported from is here as of this
  writing:
  http://sourceforge.net/p/gpredict/code/ci/master/tree/src/sgpsdp/sgp_in.c#l139
  g_ascii_strtod() is likely what gpredict uses to solve this.