Pip packaging for OM10 with running examples

[jiwoncpark]

Hi Tom!

I realized that packaging LensPop is important for packaging OM10, which uses LensPop to paint lensed quasar systems, and also SLRealizer, which has OM10 as a dependency. So I've put together a version of pip packaging that

• does not break any imports
• is compatible with the example scripts in the README
• runs tests continuously with Travis CI, where the tests are 1) the fortran deflection angle code (to see if it compiles), 2) your example scripts with 0.0001 of the sky, and 3) a test-demo I added which checks only for portions of LensPop that OM10 depends on, i.e. stellarpop.tools, lenspop.population_functions, and lenspop.distances. It's up to you to decide whether fix minor typo in module name #3 belongs here or in OM10; I put it here for now because it was my main motivation for working on this PR. :)
• fixes minor deprecation errors, typecasting bugs
• makes division, import, and print functions Python3-compatible