[PTFM-11714] Fix jq build on Mavericks by adding -lgcc_eh
Code review fixups on 0939fee

* Verify filename is set correctly
* Test with both initializing from a filename and a file obj
* Remove unused local variable creation_kwargs
* Add and reorder some comments for clarity
Unplug stdin in subprocess to avoid test hangs

Thanks to @kislyuk
Remove calls to "readlink -f" which isn't present on Mac.
Add libboost1.55-all-dev and maven2 to Debian build deps
PTFM-11709: dxpy.DXObject: Do not mask API errors as AttributeError
dxpy.DXDataObject: Do not delete _dxid and _proj (just reset to None) when object is removed
Test fix: Assert DXAPIError instead of AttributeError under new behavior
Test fix for new behavior (IDs are None after removal)
PTFM-11707: make dxpy constructors throw errors on bad IDs

Also refactor the methods to streamline ID verification and other common
get and set methods.
Allow localjob IDs in DXJob handler, and fix a test error that was previously masked
Typo fix
Changelog and version updates for v0.97.0
Only add -lgcc_eh when GCC is not emulated by LLVM
Refactoring: extract method _ensure_http_threadpool.
Don't unnecessarily invalidate readahead buffers.

Since the FS API is stateless (it receives the offset and length on
every request), it will end up performing lots of no-op seeks for
sequential access patterns (e.g. read 64k of data starting at 0, then
64k of data starting at 64k-- but on the second read, the cursor was
already at 64k). Since each of these requests could lead to its own
chain of read-ahead requests, we could end up downloading some or most
of the file more than once!

This change attempts to detect this pattern and avoid invalidating the
response and request iterators in that case.
Lower ramp factor to reduce contention when starting a new stream.

This lowers the ramp factor (from 4 to 2) and also only ramps up the
size on every 4th request (instead of every request).
Issue read requests on the file that has the least data prefetched.
[PTFM-11351] Warn if built applet has no I/O spec
Unicode fixes for dx-build-app