Miscellaneous Fixes

[crstngc]

This PR

• Closes Elephant example #1 , by determining the path to the data in the examples using the current working directory.
• Closes Simple 2D LFIS #2 , by adding a default base distribution in LFIS. This uses a multivariate normal distribution as default.
• Closes Create .gitignore #3 , by including additional patterns for .gitignore.

[dblueeye]

• Example problems

  • Reviewed the path-dependent data-loading
  • Tested all three (elephant_skeleton2D_HMC.py, ionosphere_SMC.py, sonar_SMC.py) under / and /examples/, all passed

• simple2D-LFIS.py fix

  • High-level review of the refactoring of the code
  • Tested the code, passed