Add ability to read IO types

This allows reading directly from S3 using AWS.jl

```julia
using JBDF
using AWS
using AWS.S3

# Local control file
dats, evtTab, trigs, statusChan = readBdf("BDFtestfiles/Newtest17-2048.bdf")

# Read file from AWS
env = AWSEnv(xxx)
bkt = "xxx"
fle2 = "BDFtestfiles/Newtest17-2048.bdf"
resp = S3.get_object(env, bkt, fle2);
dats2, evtTab2, trigs2, statusChan2 = readBdf(resp.obj)

# Do the files match
println(isequal(dats, dats2))
>>> true
```