added config param for whether user has consent
added params for default config and consent
updated cli parsing and added informed consent

updated cli parsing so that
1) we use a default config file if available
2) all of the options, except --config, are mutually exclusive
3) added option for informed consent
4) added logic for informed consent stuff
updated backend to create consent url
bug fixed config stuff so it actually works
updated to use urlsafe format for b64 encoding
removed some code left over from an old version
Merge pull request #68 from ben-jones/add_informed_consent

Add informed consent
added test subsetting for the client
more meaningful random subsetting config labels
Merge pull request #75 from rpanah/random_test_subset

Random test subset
updated backend error handling

1) added exception catchers on each function that talks to backend
and had them reraise exception so that we can get a call stack

2) added break statements whenever an individual result upload or
experiment download fails
removing second remove to prevent duplicate del
updated backend error mssgs to be more readable
updated backend formatting