Added sig_gen module with analog SignalGenerator
sig_gen: Corrected wave generation functions
Connector: __repr__ will return analog voltage if it is in analog mode
sig_gen: Minor docstring fixes and additions
added try-catch to handle interpreter shutdown exceptions
added signal generator tests
sig_gen: improved efficiency based on timeit tests. Used Constant value instead of pulling math.pi and voltages are set directly by accessing the voltage attribute
sig_gen tests: Sampling done only at thread pauses; Testing accuracy down to 10mv; Increased freq to reduce testing time.
sig_gen: Fixed error in AM modulation
Added AM Synthesis in docs
Merge pull request #249 from rvraghav93/signal_generator

Analog Signal Generator - Sine, Square, Ramp (  Sawtooth ), Triangular & TTL