add chapter one, figures and references

fig/general_intro/png/nicotinic_interactions.png

fig/general_intro/png/pharynx_muscle.png

fig/general_intro/png/phrmacophore_seq1.png

fig/general_intro/png/phrmacophore_seq2.png

fig/general_intro/png/receptors_2.png

fig/general_intro/png/synapse.png

fig/general_intro/png/synapse_general_2.png

fig/intro_2/Thumbs.db

fig/intro_2/cuticle2.jpg

fig/intro_2/cuticle_1.jpg

fig/intro_2/life-cycle.jpg

fig/intro_2/life_cycle.jpg

fig/intro_2/motility.jpg

fig/intro_2/vulva.jpg

fig/methods/AI_FORMAT/EPG_set-up.ai

fig/methods/AI_FORMAT/Gateway_Cloning.ai

fig/methods/AI_FORMAT/WHOLE_AND_CUT_HEAD.ai

fig/methods/AI_FORMAT/WHOLE_AND_CUT_HEAD_2.ai

fig/methods/AI_FORMAT/WHOLE_worm.ai

fig/methods/AI_FORMAT/cut_head.ai