1.4.0 - RC1

I've assembled the PRs tagged for 1.4.0 on my develop branch, and would like to merge them upstream. Change summary is as follows:

- Fix bug #63 (PR #64)
- Fix bug #41 (PR #60)
- Fix bug #65 (PR #66)
- Fix bug #69 (PR #72)
- Fix bug #42 (PR #62)
- Correct deltaV & time calculation for NASA (ModuleEngineFX) engines (PR #74)
- Implement feature #77

If I've missed anything from this list that we said we would include, or if you have any other feedback, please let me know.