Move to sbt 0.13
Avoid NoSuchElementException from chisel-tutorial LFSR16

Duplicate nearby code that checks for null clocks or clock domains
before trying to emitPrintfs.
Add "--emitTempNodes" command-line option

As part of verifying the correctness of the LLVM backend I am
currently running a diff between the VCDs that Chisel's C++ backend
emits and those that my toolchain emits.  For some larger designs
there is so much computation that goes on inside temporary nodes it's
a bit hard to figure out exactly what's going on without them in the
VCD file.

This patch adds an "--emitTempNodes" command-line option, which emits
these temporary nodes into the VCD file.  Note that "--emitTempNodes"
implies "--debug" since it feels silly to emit these temporary nodes
without emiting the rest of the internal nodes.

This probably isn't that useful for users, but I can see how it'd be
nice for debugging Chisel internals.
Merge branch 'master' of https://github.com/ucb-bar/chisel
Revert "Move to sbt 0.13"

This reverts commit 5fd29183c8e0ffa7dbb08c8fe69d8b4b410b54ca.
Remove fields index and value from Node

This way, Bundles may contain fields named index and value.
Fix very long compile times for init_mapping_table

The culprit was repeated construction/destruction of std::strings.
Instead, pass const char*s through the constructors until the std::string
truly does need to be constructed.
Speed up VCD compilation and dumping

Split VCD dump into multiple functions; get rid of strlen call; use much
shorter variable names in output
Only report NO UPDATES ON REG if the reg is used
Fix failing tests
Make assertions respect when statements
Fix setName on I/Os