fixes problem with spaces in ferret_getdata

Now only
`%ferret_getdata sstdict=sst`
will work. If you have some spaces between variables like this
`%ferret_getdata sstdict = sst`
or this 
`%ferret_getdata sstdict= sst`
 parsing of the input will fail.

This commit fixes this problem. I only was able to test on Python 2.7, so not sure if it will brake something on Python 3.

Hope it helps. 
Many thanks for the great extension!