WIP: change the setup for path_diversity project

[jJasonWang]

See the last checklist in #122.

In this pull request:

• I changed the way to import the function from the package. The way to call the function will be path_diversity.function. (import the module by from mousestyles import path_diversity)
• I created a pytest.ini to avoid the UnusedImport error for style checking.
• I also changed the tests and function name to make it more robust and consistent. (for path_index and path_filter)

@aksam-ahmad, @alannaiverson, @jcpalumbo3, @sicihuang, @togawa28.
Please help me review the file you created. All the files which used the functions in path_diversity project should have the from mousestyles import path_diversity. Also, all the function should be called by path_diveristy.function. Thanks.

@peterasujan, can you help me double check the setup for pytest.ini is correct? Thanks.

[coveralls]

Coverage increased (+0.08%) to 77.42% when pulling 279f775 on jJasonWang:path_diversity-issue122 into 8089c17 on berkeley-stat222:master.

[coveralls]

Coverage increased (+0.08%) to 77.42% when pulling abbc93c on jJasonWang:path_diversity-issue122 into dfdf5c3 on berkeley-stat222:master.

[coveralls]

Coverage increased (+0.08%) to 78.262% when pulling e51b1ac on jJasonWang:path_diversity-issue122 into 9a6534e on berkeley-stat222:master.

[jJasonWang]

@jarrodmillman. Can you help me check this pull request? I might not be able to work on this until 5 pm today. I think that if travis-CI and testing pass, we are ready to merge it.

It is just the setup for path diversity project. I changed it to the way the behavior project setup.

[jarrodmillman]

@jJasonWang Sure, I'll take a look.

[coveralls]

Coverage increased (+0.08%) to 78.262% when pulling 9e05bd4 on jJasonWang:path_diversity-issue122 into 7c257a8 on berkeley-stat222:master.